Finding Suitable Seed Guidelines for Locating Suitable Seeds

North Central Forest Experiment Station 1 .01

Finding Suitable Seed

One reason black walnut plantations may grow poorly or not at all is the use of seedfrom the wrong places. Planting success and genetic gains in growth depend partiallyon locating planting stock that both withstands the winter and grows rapidly, traitsstrongly influenced by geographic origin of the seed. Choice of seed sources can,therefore, affect the economic return from black walnut plantations. Research hasshown that 10- to 20-percent gains in height and diameter growth are possible inmost locations by using more appropriate sources of seed.

Guidelines for Locating Here are some guidelines for locating suitable seed sources:Suitable Seeds

1. Collect seed from areas 100 to 200 miles south of your planting site. Trees ofsouthern origin tend to grow faster than local or northern trees.

2. In the northern part of the walnut range where winter hardiness may be a problem,use only seed that originated within 100 miles of your planting site or mix non-localseed with local seed. To avoid loss of potential growth, never plant seed from morenortherly sources.

3. Use only seed from western sources in the western part of the black walnut range.In general, seeds of eastern origin have not grown well in the west.

4. In other parts of the range, there seems to be little advantage to using seed fromeast or west of the planting site. To be safe, plant only seed from within 200 mileseast or west of the intended site.

if you do your own collecting in a specific geographic area, be sure to collect seedfrom several trees in as many stands as possible. If you plan to purchase seed froma specific area, specify that the seed must have been collected from many trees. Thiswill ensure genetic diversity and provide greater opportunities to select and favor fast-growing, high-quality trees and to remove poorly formed, slow-growing trees as theplantation develops.

Whether you collect your own seed or purchase it, keep detailed records on the originof the seed. You should record latitude, longitude, elevation, legal description, and ex-act geographic location of the collection area as well as the number of trees includedin each collection. This information will be helpful if you should ever want to collect inthe same area again or to avoid it because trees from the area have not grown aswell as those from other locations.

Knud E. Clausen

North Central Forest Experiment Station 1.02

Seed Handling

Walnuts are usually collected in the fall or early winter shortly after falling or beingshaken from the tree. Because they are a favorite food of squirrels and other rodents,ripe walnuts should be collected as soon as possible to minimize losses. When ripe,walnut husks are yellowish green to dark brown. Once off the tree, walnut seeds mustbe handled several times before they’re ready to be planted. Remember: wear rubbergloves when handling walnuts. The husk material can severely irritate and stain yourskin.

1. Husk Although walnuts may be sown with intact husks, they are easier to handle withouthusks. If you plan to store walnuts, husk them as soon as possible, while they’re stillfirm. Here are three ways:

l Remove husks with mechanical hullers similar to corn shellers (easiest method buthullers are not always available to small landowners).

l Mix equal volumes of nuts and water in a cement mixer; blades in the cementmixer remove husks when the mixer is turned.

l Drive over walnuts repeatedly with a small car or pickup truck until the husks arecrushed.

If husks remain on stored nuts, heat builds up and the nuts become less viable. Forthis reason, keep unhusked walnuts in porous bags (like burlap sacks) until the husksare removed. With time, the husks dry out and harden, making them even more dif-ficult, if not impossible, to remove.

2. Test for Viability Within 3 days after husking, immerse walnuts in water to separate filled and emptyseeds (fig. 1). Filled seeds sink and will probably germinate; empty seeds float and

3. Stratify

4. Store

should be discarded. Do not allow walnuts to dry out before testing them-all dryseed will float. Drain filled seeds by placing them on a wire screen for about 15minutes. They will then contain the proper moisture content (about 30 percent) foreither stratification or storage.

Freshly gathered seeds are dormant and require 3 to 4 months of cold stratification togerminate properly. Note: stratification will not work with seeds that have been allowedto dry out. Seeds of northern origin may require longer periods of cold treatment thanthose from more southerly sources. Small seedlots are commonly stratified by holdingnuts for 90 to 120 days in moist peat or sand at 34* to 41° F (2O to 5O C) in 4-milplastic bags closed with wire ties. Alternating daily temperatures between 37” and 52OF (3O and l l ” C) results in even greater and more uniform germination. Or, nuts maybe stratified by storing them in well-drained outdoor pits from December throughMarch (fig. 2). Construct the pits by alternating single layers of nuts and 2-inch layersof sand. Cover with at least 6 inches of soil. Pit depth depends on the number ofnuts to be stratified, but most pits are 3 feet deep.

Figure 2.-One way to stratifynuts is to store them betweenlayers of sand in a well-drainedo u t d o o r p i t .

Because large nut crops may occur only every 2 to 3 years, some walnut seed has tobe stored for sowing during poor seed years. Successful seed storage depends onproper seed moisture content. For example, walnut seed may be stored at subfreezingtemperatures for up to 1 year if the seed moisture content is reduced to 17 percent.However, if husked nuts are to be stored at 37O F (3O C), then moisture contentshould be between 20 and 40 percent. Here’s how to determine moisture content:

Moisture content =Wet weight - Oven dry weight

Wet weightx 100

5. sow

You can use this formula with a sample of only 5 nuts. Obtain ovendry weight byweighing nuts after cracking and leaving shells and nuts in an oven at about 220’ F(103O C) for 16 hours.

Walnut seed stored at subfreezing temperatures at reduced moisture content must besoaked to increase the moisture content to approximately 30 percent. It must then bestratified before sowing.

Although stratified seed can be sown in the spring, most nurseries sow walnuts in thefall to avoid filling valuable storage space with large bulky seed. Seedbeds containingfall-sown walnut must be mulched and covered with wire cages to minimize predationby rodents. Walnuts are usually sown in the nursery at a depth of 1 to 2 inches at arate of around 8 sound seeds per square foot (86 sound seeds per square meter). Inaddition, walnuts may be sown directly in the field, avoiding the nursery altogether(see Note 2.03: Direct Seeding).

George Rink


Growing Containerized Seedlings

Growing walnut seedlings in containers can give them a better start than plantingthem as bare-root seedlings or seeds. These benefits include:

1. High-value seedlings can be protected from predation and adverse weather whengrown in a greenhouse.

2. Containerized seedlings can be outplanted later in the growing season than bare-root seedlings.

3. Containerized seedlings have an extensive lateral root system that may allow themto adapt to adverse sites more quickly.

This Note is meant to serve as a general guide for the small landowner or nurseryoperator. For large-scale commercial production of containerized walnut, you shouldconsult texts such as How to Grow Tree Seedlings in Containers in Greenhouses byRichard W. Tinus and Stephen E. McDonald (1979, USDA Forest Service GeneralTechnical Report RM-60, 256 p.) available from the Rocky Mountain Region of Stateand Private Forestry, Box 25127, Lakewood, CO 80225.

Facilities To grow containerized walnut, you will need access to a shadehouse and/or agreenhouse. Shadehouses are bird- and rodent-tight structures that reduce the sum-mer air temperature below what it would be in direct sunlight. Shadehouses areusually covered with a fabric that provides 30- to 50-percent shade, and they are usedmost frequently to harden-off or over-winter seedlings. Greenhouses, on the otherhand, are relatively air-tight structures covered with transparent materials and equip-ped for controlling supplemental lighting, air circulation, temperature, and wateringschedules. Typically, they have rigid frames and are covered with glass, film plastic, orrigid plastics.

When growing containerized seedlings in a greenhouse, you should have the followingequipment:

1. A hygrothermograph ($200 to $400) to provide a 24-hour-a-day record of airtemperature and relative humidity.

2. A pH meter ($100 to $200) to measure the pH of the watering solution and thesolution leaching from the containers.

3. A conductivity meter ($100 to $300) to measure the salt content of the containerleachate and indicate when salts from excessive fertilization are accumulating inthe growing medium.

4. A programmable repeating timer ($50 to $100) to control the supplemental lightingand photoperiod.

5. Tensiometers ($50 to $100 each) or bimetal moisture probes ($10 to $15 each) tomonitor the moisture content of the growing medium. Also, platform scales can be

used to compare the current weight of moist containers with the weight of dry andsaturated containers.

Suitable Containers Container size and shape strongly influence seedling growth. Too small containersresult in large tops and small rootballs (a high shoot:root ratio). Plastic pots are usual-ly equal in depth and diameter and are unsuitable containers because they don’t haveenough space for the developing taproots. Several manufacturers have designedspecial containers for tree seedlings (table 1). Most of these containers are typically 10times longer than wide with vertical ribs or grooves to prevent lateral roots fromspiralling.

Table 1.-Manufacturers or distributors of containers suitable for growing walnutseedlings

__-..-_____---..Common name1 Container Container Biodegradable

Supplier of container material volumes container

(cm3)- - - . . . . - ..____.---.- __-United Asia Trading Co. Paperpot Special 650 Yes3840 Crenshaw Blvd. paperLos Angeles, CA 90008(USA distributor)

J. M. McConkey Co., Inc. DEEPOTF? 0. Box 309Sumner, WA 98390

High densitypolyethylene

656 No

Spencer-LemaireIndustries, Ltd.

9160 Jasper Ave.Edmonton, AlbertaCanada

RootrainersSuper-45’s

Polystyrene 738 No

Tree Tech, Inc.P. 0. Box 86Mason, Ml 48854

Plant bands Paper with Any size Yesor withoutpolyethylenecoating

‘Trade names used in this note are for your convenience and do not constitute an implied orin tended endorsement .

Containers can be either biodegradable or rigid. Rigid containers are designed so thatthe seedling rootball and plug of growth medium can be removed intact. Before rigidcontainers are reused, they should be washed, surface sterilized in a lo-percenthousehold bleach solution (0.5-percent sodium hypochlorite) for 20 minutes, andthoroughly rinsed.

The size of container you choose depends on the length of time seedlings will be inthe containers and the size of seedlings desired. Containers with volumes between600 and 2,000 cm3 are suitable for growing succulent seedlings for outplanting in thelate spring or early summer. Larger containers are usually required for seedlings thatwill be overwintered in the containers. Containers larger than 4,000 cm3 wastematerials and valuable bench space, and walnut seedlings in them are unlikely togrow sufficient roots to hold the growth medium together.

Growing Medium Sphagnum moss peat mixed with 1 to 2 volumes of vermiculite or perlite produces alightweight growth medium that possesses many ideal characteristics. Sphagnummoss peat gives the medium the desired water holding capacity and fibril strength tohold the medium together. Horticulture grade #1 or “attic fill” vermiculite provides thenecessary buffering capacity, is high in ion exchange capacity, and has a high porevolume. Because perlite will not compress when wet, coarse (1- to 3-mm particle size)perlite is a better bulking material than vermiculite; however, perlite has little or nobuffering or ion exchange capacity. A shallow layer of perlite over the growth mediumprotects the germinating seed from the sun, provides a droughty surface to reducealgal and fungal growth, and allows water to penetrate better into the medium.

Homemade growth medium using topsoil, compost, or unsterilized peat should besteam sterilized at 180° F for 30 minutes or chemically sterilized with formaldehyde,chloropicrin, methyl bromide, or Vapam@ ? Chemical sterilization should only be doneby trained individuals. The chemical must be thoroughly dissipated from the mediumbefore use to prevent trapped residual chemical from injuring germinating seed.

Thoroughly mix and moisten the medium before filling the containers. The mediumshould not be allowed to dry out because peat is difficult to rewet when in the con-tainers. Do not mix water-soluble fertilizers in the medium because they leach outbefore seedlings are large enough to use them. Slow-release fertilizers can be addedif seedlings will be outplanted before the hardening-off stage.

Seedling GrowthStages andRequirements

Germination.-Fully stratified seed (see Note 1.02: Seed Handling) should be preger-minated to minimize the number of empty containers. To pregerminate seed, place250 to 500 nuts in large 2- to 4-mil black polyethylene bags and set them in a warmshaded area. Check bags every other day for seeds with split sutures and emergingradicles.

Plant pregerminated seed on its side and cover with 1 to 2 inches of growth mediumor perlite before moving containers into the greenhouse. Set containers on racks or onpainted surfaces containing copper carbonate to “prune-off” emerging taproots andlateral roots. Seedlings should emerge within 7 to 10 days, depending on temperature.During this stage, maintain daytime temperatures around 75O F (65 to 80° F permissi-ble range) and a relative humidity of 70 percent (50 to 90 percent permissible range).Providing 8 to 10 watt/ft* (450 lux) supplemental incandescent light for 1 minute out of

‘Mention of trade names does nor constitute endorsement by the USDA forestService.

3

every 15 minutes throughout the night is also beneficial. Water containers during theday as needed to minimize the time water droplets stand on the new leaves or growthmedium surface.

Juvenile Growth Phase.-After the first leaves have expanded, raise the daytimetemperature to 83O F (79 to 86O F permissible range) and the night temperature to72O F (66 to 82O F permissible range), lower the relative humidity to 60 percent (50 to80 percent permissible range), maintain supplemental lighting, and begin fertilizingwith each watering, using a complete, high nitrogen fertilizer. Water to excess andrinse foliage with clear water at each watering to avoid leaf damage and reduce algalgrowth on containers. Water leaching through containers should have a pH within 0.3to 0.4 units of the watering solution and a conductivity reading below 1,800 mhos.Begin checking daily for pests. Pest problems start small and grow rapidly. Treat in-fested areas immediately and begin regular weekly spraying. Rotate use of pesticidesto retard development of resistance.

Exponential Growth Phase.-At this stage, seedlings will become tall and slenderwithout a visible terminal bud. Maintain the same growing conditions as for thejuvenile growth phase. Increase air circulation to prevent air from stagnating in seed-ling crowns. Check that all seedlings are being uniformly watered and rootballmoisture stress levels are between 0.5 and 3.0 bars for maximum height growth.Elevating COn levels between 1,000 and 2,100 ppm during the daytime when thevents are closed will increase height growth of walnut seedlings. The CO2 level canbe raised by using specially designed propane or natural gas burners or by pilingfresh manure in one corner of the greenhouse. At the end of this phase, seedlingscan be outplanted in late spring or early summer on moist, well-prepared sites;however, the succulent stems are easily broken.

Bud Development Stage.-During this stage, seedlings are forced to set a terminalbud while growth in caliber, roots, and buds continues for another 3 to 5 weeks.Water containers heavily to remove excess nitrogen from growth medium, then allowthem to dry until seedlings wilt for 12 to 24 hours. After this, fertilize the containerswith each watering, using a complete fertilizer high in phosphorus and potassium.Seedlings can now be moved to a shadehouse if night temperatures are well abovefreezing. If seedlings are left in the greenhouse, discontinue the supplemental lightingand elevated C O * levels and gradually reduce the temperatures. Seedlings outplantedat the end of this phase in late summer or early fall when frosts are not expected willnot reflush until the following spring.

Co/d Hardening Stage.--During this stage, temperatures are brought close to freezing,and seedlings begin to develop leaf abscission layers. After 2 weeks at lowtemperature, seedlings can tolerate some frost; and after another 2 to 3 weeks, thestems can remain frozen for weeks at a time if protected from dessicating winds. Therootball should not be allowed to freeze. Place sawdust, straw, or coarse peat alongthe sides and over the top of the containers to protect rootballs from freezing. Justbefore outplanting cold-hardened seedlings, thoroughly water the seedlings with acomplete, high nitrogen fertilizer.

J. W. Van Sambeek


Seedling Sources

Black walnut seedlings may be obtained from most State nurseries in areas wherewalnut is found naturally. Contact your local extension agent or State forester to findout if walnut seedlings are produced in your State, how much they cost, and how toorder them. Some State nurseries only sell seeds, not seedlings.

Seeds or seedlings may also be obtained from commercial nurseries. A list of com-mercial nurseries is provided below.

Note: prices differ substantially depending on whether seedlings are grafted varietiesselected for fast growth or “run of the woods” seedlings grown from seed.

Commercial Nurseries Bountiful Ridge Nurseries, Inc.Box 250Princess Ann, MD 21853

Burgess Seed & Plant Co.905 Four Seasons RoadBloomington, IL 61701

W. Atlee Burpee300 Park Ave.Warminster, PA 18974

Cascade Forestry Service, Inc.Route 1Cascade, IA 52033

Central Indiana Walnut Growers, Inc.1818 Arrowhead DriveWest Lafayette, IN 47906

Charley’s Nut Tree NurseryC. A. RichcrickRD 10, Box 155York, PA 17404

Krider NurseriesI? 0. Box 29Middlebury, IN 46540

Earl May Seed & Nursery Co.Shenandoah. IA 51603

Mellinger’s Inc.2310 W. South Range RoadNorth Lima, OH 44452

J. E. Miller NurseriesCanandaigua, NY 14424

Neosho Nurseries900 North CollegeNeosho, MO 64850

The Nolin River Nut Tree NurseryRoute 2, Box 330Upton, KY 42784

Pennsylvania Nut NurseryGlenn L. Helms, PropagatorHellertown, PA 18055

Saginaw Valley Nut Nursery705 Adam StreetSaginaw, MI 48602

Emlong Nurseries, Inc.Stevensville, Ml 49127

Environmental CollaborativeP. 0. Box 539Osseo, MN 55369

Farmer Seed & Nursery Co.Fairbault, MN 55021

Earl Ferris Nursery811 4th Street, N.E.Hampton, IA 50441

Henry Field Seed & Nursery Co.Shenandoah, IA 51602

Louis Gerardi NurseryRR 1, Box 144O'Fallon, IL 62269

Girard NurseriesI? 0. Box 428Geneva, OH 44041

W. Greiner & Sons NurseryI? 0. Box 70Mulvane, KS 67110

Gurney Seed & Nursery Co.Yankton, SD 57078

H. G. Hastings, Co.Box 4274Atlanta, GA 30302

Inter-State Nurseries, Inc.Hamberg, IA 51644

Kelly Bros. Nurseries, Inc.Dansville, NY 14437

Elwood Kerstetter2743 Boas StreetHarrisburg, PA 17103

Savage Farms NurseriesP. 0. Box 125, PL-1McMinnville, TN 37110

St. Lawrence NurseryBill MackentlyRD 2Potsdam, NY 13676

Stark Bro’s NurseriesBox 83457 ALouisiana, MO 63353

Summer View NurseryRt. 2, Box 210McMinnville, TN 37110

Vanbourgondien Bros.Box A 245, Rt. 109Babylon, NY 11702

Vans Pines, Inc.West Olive, Ml 49460

Warren County Nursery, Inc.Rt. 2, Box 204McMinnville. TN 37110

Waynesboro NurseriesP. 0. Box 987Waynesboro, VA 22980

Wayside GardensHodges, SC 29695

Leslie H. Wilmoth NurseryRt. 2, Box 469Elizabethtown, KY 42701

Zilke Brothers NurseryBox 8Baroda, Ml 49101

George Rink


Black walnut is a difficult species to propagate vegetatively. The most successful pro-pagation methods involve grafting-either grafting indoors with containerized rootstock(bench grafting) or grafting on established seedlings or trees (topworking).

Materials Required l A very sharp knife made of high-quality steel that will hold a sharp edge. Graftingsuccess depends on the grower’s ability to make long, smooth cuts with a singlestroke of the knife.

l Grafting rubber or budding strips for binding the graft union.l Some semipermeable material such as grafting wax, paraffin, or Parafilm@l to

cover the graft and keep the scion from drying out.

Bench Grafting

Budding

Two types of bench grafting-side and cleft grafting-use dormant scionwood (1-year-old branch tips from the desired cultivars) and actively growing seedling rootstocks.The grafting method you choose depends on your ability to match the cambiums(single layers of cells between the bark and the wood) of the scion and rootstock. Forboth methods:

1 . Collect dormant scionwood in late winter (January to March) when the tissue isnot frozen.

2. Bundle together scionwood from the same tree, label it, and then store it dry inlabeled plastic bags in a refrigerator until rootstocks are ready for grafting.

3. Select large 1-O seedlings for the rootstocks and plant them in l/2- to l-gallon con-tainers using a well-drained potting medium (see Note 1.03: Growing Containeriz-ed Walnut).

4. Graft rootstocks when the buds along the stem begin to elongate or a few smallleaflets are present.

Cleft (wedge) grafting.-This graft is best used on scionwood and rootstocks of thesame diameter (fig. 1).

Side grafting.-With side grafting, you can adjust the depth of cut on the rootstock tofit a variety of smaller scionwood diameters (fig. 2).

Budding is a form of grafting where a bud and the surrounding bark are slipped fromthe scionwood and grafted to the rootstock. Budding can be done from the timerootstocks begin to leaf out until new shoots are 12 inches long.

1. Prepare the rootstock by making two parallel cuts about one-half inch apartthrough the cambium but not into the wood about 4 inches above the groundThe cuts should be about 1112 inches long.

‘Mention of trade names does not constitute endorsement by the USDA ForestService.

Figure l.-Cleft (wedge) grafting.

1. Prepare the basal end of the scionwood by cutting it evenly on both sides to form a long, uniformlytapered wedge about 2 inches long.

2. Cut off the stem of the rootstock where its diameter is equal to the diameter of the scionwood (upperleft).

3 . Make a vertical cut down the middle of the stem about 2 inches deep.4. Insert the scionwood wedge into the cut until the cambiums match on both sides (upper right).5. Tie the graft with a budding strip around the base of the graft union and wrap overlapping each turn

to prevent the tissues from separating as the area calluses over (lower left).6. Tie budding band off by inserting end through last wrap, then paint entire graft with grafting wax or

softened paraffin to prevent the scion from drying out (lower right).7. Complete the graft by clipping off the scion, leaving two dormant buds.

Figure 2. -Side grafting

1. Cut a piece of scionwood off 2 inches below an intact bud.2. insert the knife into the bark just below the bud and make a long, smooth diagonal cut through the

center of the base.3. Make a similar cut on the opposite side.4. Prepare the rootstock by making a single diagonal cut’ about 1% inches long near the base of the

stem so that the width of the cut tissue matches the diameter of the scionwood (upper center).5 . Insert the scionwood into the cut with the bud on the side away from the rootstock (upper right).6. Tie the graft union with a grafting rubber or budding strip (lower left and lower center) and then cover

it with soft paraffin, grafting wax, or Parafilm to prevent the scionwood from drying out (lower right).7 . About 7 to 10 days after grafting, remove the rootstock stem above the scion.

3

2. Make two perpendicular cuts to remove the entire piece of bark or remove theupper two-thirds of it to create a flap.

3. To prepare the bud, take the dormant scionwood and start a cut about one-halfinch above a bud, cutting through the cambium and along the wood until aboutone-half to three-fourths inch below the bud. The bud chip should be a nearduplicate of the cut on the rootstock.

4. Slip the bud chip into the cut on the rootstock or under the flap if it was notremoved and align cambiums.

5. Starting below the bottom of the chip, spirally wrap masking tape around thegraft, just missing the bud.

6. Repeat the operation starting from above the graft in the opposite direction.7. Using waxed string, spirally wrap the graft three times below the bud, cross over

behind the bud, and spirally wrap three more times to the top of the graft.8. Repeat the procedure in the opposite direction.9. If excess bleeding occurs around the graft, drill one or two small holes through

the base of the rootstock.10. In 2 to 3 weeks, cut off the original stem 12 inches above the graft.11. Perodically rub off all buds on the stub except the grafted bud.12. When the new growth is 2 to 3 inches long, make a vertical cut through the

string and masking tape on the stub opposite the bud.13. When the new growth is 6 to 8 inches long, tie it to the stub to support it and in-

duce vertical growth.

Bench grafting aftercare.-Keep greenhouse temperatures between 65 F and 90’ Fto promote rapid callusing and new shoot growth. Twice weekly, all buds sproutingalong the rootstock stem must be removed to prevent competition with scion growth.Keep humidity as high as possible without directly misting or sprinkling the graftunion. Grafts should be held in the greenhouse until the union calluses over andleaves begin to expand. Outplant grafted seedlings as containerized seedlings after alldanger of frost has passed; or move them to a shadehouse and hold them over untilthe following spring.

Topworking established rootstocks-Topworking refers to grafting onto rootstocksalready established in a plantation or nursery bed. Topworking does not require use ofa greenhouse. All three methods of grafting can be used to topwork establishedwalnut seedlings and saplings; however, budding usually gives the best results.

Whichever grafting method you use, keep these basic principles in mind:

1. Black walnut cuttings should be grafted to black walnut rootstocks.2. Long, smooth cuts with a very sharp knife are the secret to successful grafting.3. The cambiums of the scionwood and of the rootstock must be aligned as closely

as possible.4. Optimum temperatures to promote callusing of the graft union are between 80°

and 8 Y F.5. The scionwood and graft union must not be allowed to dry out.

J. W. Van Sambeek


Black Walnut Cultivars

Cultivars are the products of vegetative propagation of a clone, of selection of a race,or of controlled breeding worthy of a separate name. More than 400 black walnutcultivars have been named in the past century, most for increased nut yield or quality.Walnut growers interested in producing nuts might achieve better yields by plantingcultivar seedlings instead of bed-run nursery seedlings if a cultivar can be found tomatch their needs. Cultivars for timber, a recent development associated with risingprices for veneer logs, are also described in this Note.

Cultivars for Nuts The more popular cultivars currently being commercially propagated and grown fornuts are listed below with permission! States and provinces in parentheses indicatethe cultivar’s place of origin.

BURNS (Ontario), small, thin-shelled nut that has an exceptionally highkernel percent. All kernels can be recovered on the first crack, mostly ashalves.

EDRAS (Iowa) has high kernel weight and exceptional total kernel percent.The high percentage of kernels recovered at first crack indicates goodcracking quality. Above-average survival in plantings.

EL-TOM (Ohio), a cross between Thomas and Elmer Myers, is character-ized by a thin shell, high kernel percent, and light kernel color.

EMMA K (Illinois) has a thin shell and cracks out a high percentage ofkernels. This cultivar bears heavily in southern Ontario, but not all the nutsfill well in heavy crop years. Nut flavor is reputed to be excellent, but thecultivar has not yet been extensively tested. The tree has a spreadingcrown.

GRUNDY (Iowa) ranks high in all kernel traits: total weight, first-crackpercentage, and total percentage. Below-average survival in plantings. Poorproducer in Kentucky so may not be a good selection in warmer climates.

HARE (Illinois) produces a large smooth nut. The good shell structureallows a high first-crack and total kernel percentage. Easily propagated bybudding and seems well adapted to Illinois and Missouri conditions.

‘Scionwood of many cultivars can be purchased from the Nebraska Nut GrowersAssociation, Box 4644, Lincoln, Nebraska 68504.

HARNEY (Kentucky) ranks high in all kernel characteristics, but survival inall plantings has been below average.

HOMELAND (Virginia) matures early, producing large kernels that tend tobe slightly shriveled.

MINTLE (Iowa) is a small nut with exceptional total kernel percentage.Reputed to have the best flavor of all black walnuts; can be stored at roomtemperature for 2 years without becoming rancid. Survives exceptionallywell in plantings.

MONTEREY (Pennsylvania) has large kernels and high kernel percent;easily propagated by budding and grafting. Survives well in plantations.

MYERS (Ohio) is a standard cultivar noted for its very thin shell and goodcracking qualities. Exceptional total-kernel and first-crack kernel percentagesand a high recovery of quarters. Resistant to anthracnose and apparentlyadapted to southern growing conditions, but needs to be on a good siteand well cared for. At more northern locations, kernels tend to be shriveledand bearing is often erratic.

OHIO (Ohio) dates from 1915 and is well known for its fine crackingqualities. Moderately resistant to anthracnose, but highly susceptible tohusk maggot.

PINECREST (Pennsylvania) produces large kernels and a high percentageof kernels. Readily propagated by budding and grafting.

SNYDER (New York) has plump, medium-color nuts that have earned goodnut evaluation test scores when grown in New York and Ohio.

SPARROW (Illinois) cracks well with exceptional total kernel percent. Ex-cellent nut flavor and good color; very resistant to anthracnose. The nut issmall unless the tree is well grown and on a good site.

STAMBAUGH (Illinois) is a large-kerneled cultivar that bears at an earlyage. Susceptible to anthracnose leaf spot infection.

STABLER (Maryland) cracks exceptionally well. Some of the nuts developwith a single lobe. Very susceptible to husk maggot.

THOMAS (Pennsylvania) has become a well-known black walnut cultivarsince its discovery in 1881. Bears at an early age, and the large nuts crackwell with large kernels and taste good. After many years of objectivetesting, Professor MacDaniels (1974) concluded that, " . . . (no) one variety isconsistently better than Thomas.” But Thomas does not perform consist-ently from year to year or over a range of locations. Poor selection for the

Midwest. The most frequent criticism is that the nuts do not fill well,especially on trees more than 5 years old. Nuts may develop poorlybecause of early defoliation induced by anthracnose.

TODD (Ohio) bears a large nut with a smooth shell and good crackingquality. High kernel yield and kernel percent. Does not always fill well inNorthern States.

VANDERSLOOT (Pennsylvania) is outstanding for its large nut size, kernelweight, and its good cracking quality. Resistant to anthracnose leaf spot.

VICTORIA (Kentucky) has lower nut evaluation scores than other thin-shelled cultivars. Vigorous tree, resistant to leaf spot.

Cultivars for Timber In addition, the Purdue Research Foundation of Purdue University has developed thefollowing nine cultivars from selections made for good form, rapid height, anddiameter growth, primarily for faster timber production.

PURDUE 1 bears abundant crops each year with nut set on lateral shoots,a rare occurrence in black walnut. Only negative features: some suscep-tibility to anthracnose and a slightly earlier than normal leafing date.

PURDUE 2 has rapid growth, but below-average straightness. Leafs out aweek later than average, a desirable trait. Good choice if a nut crop is notnecessary.

PURDUE 3 combines rapid growth and good straightness with very lateleafing and good anthracnose resistance. Good all-around tree even thoughthe nut crop is light and erratic from year to year.

KNOX 1 is noted for rapid growth, heavy annual nut crops, and good an-thracnose resistance, but is below average in straightness. Susceptible tolate spring frosts because it leafs out nearly a week earlier than average.

LAWRENCE 1 has very rapid growth, good straightness, and excellent an-thracnose resistance. Its nut crop is abundant but tends toward alternate-year bearing.

LAWRENCE 2 doesn’t grow as fast as some of the other patents, but it isuniquely suited to plantation culture. Extremely straight and fairly short witha large diameter and relatively little taper so very firmly anchored and notsusceptible to wind damage. Very good anthracnose resistance, outstandingannual nut-bearer.

TIPPECANOE 1 is the fastest growing of all the patented trees. It has goodstraightness but is somewhat susceptible to anthracnose and producesvery few nuts.

FAYETTE 1 is fast-growing, has average straightness, and abundant butalternate-year nut-bearing characteristics. Most outstanding feature: unusual-ly strong anthracnose resistance.

FAYETTE 2 was patented for its nut production. Otherwise, it has arelatively slow growth rate and very poor straightness. It has good anthrac-nose resistance and is very late to leaf out. Produces nuts in great abun-dance each year by age 3 or 4; clusters on spur-type lateral shoots containup to six nuts.

George Rink

Funk, David T. 1979. Black walnuts for nuts and timber. In: Jaynes, R. A., ed. Nut treeculture in North America. Hamden, CT Northern Nut Growers Association, Inc:51-73.

Beineke, Walter F. 1984. Characteristics of Purdue University’s patented black walnuttrees. FNR-105. West Lafayette, IN: Purdue University Cooperative Extension Ser-vice. 3 p.


Choosing a Good Walnut Site

One of the black walnut grower’s most important decisions is where to plant thisvaluable, but sensitive hardwood. Black walnut has specific soil-site requirements thatmust be considered when locating a planting site. It grows well only on land of goodquality. Briefly, black walnuts grow best in soil that is:

l medium texturedl deep, well-drainedl not stonyl on lower north- or east-facing slopes (avoid planting on rolling, hilly ground) not

compacted.

Landform

Soil Texture

Drainage

Nutrients and pH

Natural stands of black walnut are located most frequently on bottomlands, coves, andlower slopes. In selecting your planting site, consider floodplain sites carefully-you’llneed to avoid the many clayey and heavy textured soils that often occupy such sites.On the uplands, the better planting areas are commonly located on the loweruplands, lower north- and east-facing slopes, and stream terraces. Soil moisture anddepth may limit growth on upland sites. Avoid: steep or south-facing slopes and nar-row ridgetops.

Soils in the better black walnut sites are deep and medium textured over loose, well-drained subsoils. The best soils for walnut plantings are composed of topsoils of san-dy loam, loam, or silt loam over similar subsoil textures, or sandy clay loam or clayloam. Also good are limestone soils with silt loam over clayey subsoils.

Select with caution: soils with gravel layers or bedrock within 3 feet of the surface.Avoid: coarse or heavy-textured soils that are eroded or shallow to a mottled subsoilor bedrock.

Black walnut needs an ample supply of moisture but cannot tolerate long periods ofhigh water. The soil must be well aerated to allow air movement in the rooting zone.Soil color is usually a good indicator of soil drainage. Well-drained soils have uniformshades of brown or reddish-brown from the surface to 3 feet deep or more. Avoidsoils with streaks of gray, red, or yellow, or an unpleasant odor-they’re poorlydrained.

Planting in naturally fertile soil is a more reliable way to get black walnut growth thanfertilizing poor soils. Nutrients needed by black walnut in the largest amount areavailable at pH 5 to 8. Avoid soils with acid clayey subsoils.

Other Things toConsider

When choosing a planting site, remember that walnuts grow better when protectedfrom high wind and frost.

Check out the vegetation on a prospective site before planting-it can give you cluesto the site’s productivity. For example, a sparse cover of weeds and grasses generallyindicates low fertility, erosion, or droughty conditions. The composition of the covercan also tell you about the site; sedges, for example, indicate a wet soil.

For other help in selecting suitable black walnut planting sites, consult a soil scientistor State forester who is familiar with the soils in your area.

Reference Ponder, Felix, Jr. 1982. Some guidelines for selecting planting sites. Northern NutGrowers Association Annual Report 72: 112-117.

Felix Ponder; J r .

2

Site Preparation


NOTESSpending a lot of time, effort, and money on preparing a site for black walnut mayactually save you money in the long run. The most intensively prepared sites gener-ally require the least weed control after planting.

Site preparation involves removing unwanted vegetation and/or improving the physicaland chemical condition of soil on the planting site for tree establishment and growth.Vegetation can be controlled by various mechanical, chemical, or combinationmechanical-chemical methods, depending on the density and size of existing cover,topography, soil type, and equipment available.

Mechanical Methods Mechanical site preparation should be done in the fall, and precautions should betaken to minimize erosion. On brushy clearcuts, remove brush completely withbulldozer and attachments. Then disk to reduce the impact of compaction caused byroads, skid trails, and tractor tracks. Heavy sod areas may be prepared by plowing,disk harrowing, or rototilling several times. In some cases, subsoiling may be useful todestroy plow pan layers on old field sites.

Chemical Methods Chemical methods of site preparation depend on the species, size, and density ofvegetation present. Chemicals are quite specific in the kinds of vegetation they con-trol. A list of commonly used chemicals is included at the end of this Note. Checkwith your county extension office to find which ones are registered for use in yourarea. For dense, mixed hardwoods, apply broadcast foliage or stem-foliage spray inearly summer after leaves fully develop. Apply enough herbicide to thoroughly coverleaves.

Some herbicides used in chemical site preparationI. Grass and herbaceous weeds

Refer to note on weed control.II. Woody vegetation

A. Soil treatments Suggested rate1. Fenuron 50-l 00 I bs/acre2. Tordon 10k 60-85 lbs/acre3. Tordon 101 1-4 gals/acre

B. Foliage1. 2,4-D 2 qtslacre2. Glyphosate 2 qts/acre

C. Basal-bark1. 24-D 2-3 qtslacre2. Monosodiummethane arsonate 1 ml/injection3. T r i c l o p y r l 2 qtslacre

‘Depending on formulation, triclopyr may be used as a basal spray or as a groundapplication for less selectivity

Chemicals may also be applied in the cut surface treatments listed below.

Cut stump: Thoroughly wet the surface of the freshly cut stump and the bark withchemical.

Frill-gridle: Cut through the bark around the tree, and girdle the trees by stripping aband of bark away. Spray chemicals over the area.

Tree injector: Make incision through bark and inject chemical.

Soil sterilants may be broadcast or spot applied to control non-selective hardwoodbrush. Use these chemicals carefully because they may be absorbed by roots ornearby desirable trees. Delay planting 6 to 12 months or longer because somesterilant chemicals persist in the soil. In all cases, follow directions.

In addition to killing competing vegetation, prepare the site chemically to accept thenew seedlings. Soil should be analyzed for pH, nitrogen, phosphorus, potassium,calcium, and magnesium. The pH should be between 5 and 8. Some sites may re-quire an application of lime to raise the pH.

The importance of site preparation cannot be overemphasized. Consult your Stateforester to find out if other methods of site preparation may also be appropriate.

Felix Ponder, Jr.

Prepare the Site


NOTESShould a grower plant black walnut seeds...or black walnut seedlings? There’s no oneright answer, but planting seeds offers several advantages over planting seedlings:

1. Seedlings from seeds develop normal taproots.2. Seeds are easier to store and carry to the planting site.3. Seeds can be planted in the fall or in the spring after stratification.4. Seeds of selected, high-quality trees can be planted instead of run-of-the-mill

seedlings.

However, direct seeding has some drawbacks:

1. Because of unpredictable germination, several seeds must be sown in each seedspot.

2. Seeds must be protected from squirrels and other predators.

If you’ve decided to direct seed your plantation, here are some guidelines to follow.

Before sowing seeds, prepare the planting site to kill competing vegetation (see Note2.02: Site Preparation). This can be done by cultivation (plowing, disking, or rototilling)or by treatment with a combination of preemergent and postemergent herbicides.Recommended techniques include:

1. Plow and disk the entire planting site if soil erosion will not occur.2. Spray 4-foot-wide strips, and plant the nuts down the middle of each strip at the

desired spacing, or3. Spray a series of 4-foot-diameter circles at the desired spacing, and plant seeds in

the middle of each circle. A properly squared spacing will allow for plantationmaintenance by machine in both directions.

Choose Good Seed Test the viability of freshly husked seeds by placing them in a container of water.Empty seeds will float; filled seeds will sink (see Note 1.02: Seed Handling). Crackopen a small sample of nuts (10 to 20) to determine the percentage of sound seed inyour seedlot. Viable nuts have white, sound-looking meat; non-viable seeds havebeige, shriveled kernels that are watery or give off a foul, rancid odor (fig. 1). Thepercentage of viable seeds in your sample will determine how many seeds to plantper spot. Use of the following table as a guide will result in only 5- to 20-percentblank spots.

Figure 1.-Viable nuts havew h i t e , s o u n d - l o o k i n g m e a t .

Sound seed Seeds per spot(Percent) (Number)

80-l 00 260-80 340-60 4Less than 40 5 or more

Plant the Seeds Seeds may be planted early in the fall so that the necessary chilling occurs naturally,or they can be planted in the spring if they are fully stratified (see Note 1.02: SeedHandling). Improper stratification or dry soil may delay germination until the secondyear. Fully stratified seeds can be taken out of cold storage about 1 week before plan-ting to accelerate germination. Make sure they do not dry out. Handle seeds carefullyto protect the emerging radicles.

Plant each seed about 2 to 3 inches deep with the nut laying on its side. If morethan one seed is planted per seed spot, place them at least 8 inches apart to make iteasier to remove excess seedlings at a later date. If you plan to strip spray with her-bicides in the future, plant nuts within a seed spot in a single file parallel to the rows.If you plan to spot spray, use a triangular pattern for three seeds or a square patternfor four seeds within each seed spot. Using clustered patterns helps to keep rowsstraight, minimize size of herbicide circles, and minimize amount of materials neededif you erect mechanical barriers to predation.

Protect seeds from squirrels and other predators by using mechanical barriers orchemical repellents. The cheapest and most effective repellent is a generous portionof fresh cow manure over each seed spot (see Note 5.06: Preventing AnimalDamage).

Tend the Seedlings After the first or second growing season, pick out the best seedling in each seed spotand remove the rest. Thrust a sharp spade diagonally under the unwanted seedling,cut off the shoot about 1 inch below the root collar, and pull up the shoot. (You maywant to dig up extras and transplant them to empty seed spots.) Use postemergentherbicides on unwanted seedlings with caution because spray may drift onto thedesired seedling or be carried through the root system to that seedling. When using apostemergent herbicide like Roundup’, apply it when the top growth has slowed andsoil moisture is adequate for continued root growth.

J. W. Van Sambeek

‘Mention of trade names does not constitute endorsement by the USDA ForestService.

3

North Central Forest Experiment Station 2 . 0 4

Planting Seedlings

Black walnut plantations can be established by either planting seeds (see Note 2.03:Direct Seeding) or by planting seedlings. Most plantations are established using bare-root, nursery-grown seedlings because it’s more predictable than planting seeds andbecause it’s cheaper than planting containerized stock (see Note 1.03: Growing Con-tainerized Walnut). If that’s what you decide to do, here are the steps to follow.

1. Prepare and Lay Out For timber production, spacings of 10 or 12 feet square (436 or 302 trees per acre,the Planting Site respectively) are recommended because these spacings allow room for mechanized

weed control and allow trees to reach a 5-inch average d.b.h. without thinning. Bandor spot-spray herbicides within the tree rows before planting to (1) remove the im-mediate competition, (2) mulch the soil surface, keeping soil moisture fromevaporating, and (3) leave weeds between the rows to provide some shade and windprotection (see Note 2.01: Choosing a Good Walnut Site and Note 2.02: SitePreparation).

2. Order Seedlings Obtain seedlings from a private nursery or from your State nursery through your Stateforester or local extension agent (see Note 1.04: Seedling Sources). If you orderungraded seedlings, order extra so you can cull out all seedlings with damaged ordiseased roots and the smallest 10 to 20 percent of the seedlings.

3. Prepare theSeedlings

The care you give your seedlings after they arrive from the nursery and during plan-ting will have more bearing on their survival and early growth than how they areplanted. Seedlings should be planted as soon as possible after they arrive. Openpackages when they arrive and rewet roots if necessary. Bundled seedlings can bestored for several days in a cool, shady place if protected from freezing or stored for2 to 4 weeks in cold storage (34 to 38O F) without seriously deteriorating. Stackbundles so air can freely circulate around each bundle to prevent “heating” within theseedling bundles.

Seedlings can also be temporarily transplanted into “heeling-in” trenches. Dig a V-shaped trench that is deep enough to cover the entire root system and long enoughto spread seedlings out along the sloping side. Pack soil firmly around roots, andwater as needed. Trenches should be dug in a shady, somewhat protected area andmulched to give the seedlings additional protection.

Before planting, soak seedling roots in water for 1 to 2 hours; keep seedlings moistwhen planting by carrying them in planting trays or canvas planting bags packed withmoist peat. Before planting, prune the seedling taproot to a length of 8 inches and alllateral roots to a length of 1 to 2 inches. Do not shear lateral roots off because thisreduces the number of potential sites for new root growth. Do not plant seedlingswhen there is snow on the ground, when soils are too wet, or if frost-heaving can stilloccur.

4. Plant the Seedlings Walnut seedlings can be planted using either the hole or the slit method.

Hole method.-Use a shovel, grub hoe, mattock, or post hole digger to dig a holedeep and wide enough to spread the root system out in all directions. The seedlingroot collar should be placed about 1 inch below the groundline. Layer soil back intothe hole 2 to 3 inches at a time to minimize the size and number of air pockets. Ifyou use a mechanical auger or post hole digger in heavy, wet soils, the sides of thehole can become “plastered” forming a “pot” through which the seedling roots can-not penetrate (fig. 1).

S/it method.-Make a lo-inch-deep vertical slit with a planting bar, tile spade, ormechanical tree planter. Insert the seedling taproot to the bottom of the slit and lift itslightly to spread out lateral roots. Firmly tamp soil around the roots at both the topand bottom of the slit. Air pockets, especially those at the bottom of the slit, help toreopen the soil when it dries out and shrinks. If you use a tree planting machine,make sure the slit is deep enough to prevent the seedling from forming L-shapedroots along the bottom of the slit. In addition, you should follow the machine tostraighten and tamp soil around each seedling. If the seedling is planted on a slant, asprout may originate from the root collar and replace the original stem (fig. 2).

Walnut seedlings normally must go through a brief period of transplant shock beforethey adapt and begin growing new shoots.

J. W. Van Sambeek

Figure l.-Hole method of planting large or fibrous rooted seedlings.

CORRECT METHOD FOR HOLE PLANTING

A. Dig hole slightly larger than the rootball when spread out.B. Set seedling root collar slightly deeper than top of hole, partially fill hole, and firm soilC. Fill hole, firm soil, and add loose soil as mulch.

INCORRECT METHODS FOR HOLE PLANTING

D. Seedling set too deep, hole too large.E . C o m p a c t e d r o o t b a l l , h o l e t o o n a r r o w .F. Duff and debris added to hole which may form air pocketsG. Hole too shallow and will lead to exposed roots.H. "L"- or "J"-rooted, hole too shallow.I . S e e d l i n g n o t v e r t i c a l , h o l e t o o s h a l l o w .

3

Figure 2.-Slit planting method with planting bar or tile spade.

A. insert bar straight down and pull backward.B. Push bar down at same angle to get a new bite.C. Push bar to vertical position.D. Remove bar and set seedling in hole at correct depth.E. Insert bar straight down about 2 inches behind first hole.F. Pull bar back and tightly pack soil around lower roots.G. Push bar forward and tightly pack soil around upper rootsH. Repeat steps E to G and close new hole with shoe heel.I. Firm soil around seedling with shoe heel.

4


NOTESWeeds affect black walnut trees the same way they affect other crops. They rob themof moisture, nutrients, and light. But walnut growers can use a variety of mechanicaland chemical methods to protect their trees from weeds.

Mechanical Controls Cultivation is the most effective mechanical weed control method. You can cultivatethoroughly using a tandem disc, but that may damage feeder roots. Roots will bedamaged less if you cultivate shallowly with a rototilling attachment. Begin right after“green up” in the spring, and repeat as often as necessary to keep weeds from get-ting taller than 6 inches. Time the last cultivation of the season to let vegetationrecover enough to provide erosion protection during fall and winter. Take care: astrees get larger, their lateral branches are easily torn off by equipment operatedclose-by.

Periodic mowing provides plenty of sunlight for young trees by removing the tops ofweeds and grasses; but weed roots remain actively in place. Do not substitute mow-ing for cultivation or herbicides.

Mulching with plastic, sawdust, bark, or wood chips can control weeds, but consumesa lot of time and money. It is practical only in small plantations.

Chemical Controls Chemical weed control works better and costs less than mechanical control, but mustbe done with skill and care.

Two general types of chemicals are used in walnut plantings: (1) preemergent her-bicides are applied early in the spring before seeds begin to germinate whenmoisture conditions are favorable; (2) postemergent herbicides act upon contact withthe foliage and are applied when the vegetation is growing vigorously.

Several chemicals are effective in controlling weeds in black walnut, particularly onepreemergent herbicide, simazine, and five postemergent herbicides: atrazine, amitrol,dalapon, glyphosate, and 2,4-D. These are tolerated well by black walnut, generallyavailable, inexpensive, and safe when handled and applied properly. Consult yourState forester to find out what other chemicals may work satisfactorily in walnutplantings.

The type of herbicide you need to use depends on the types of weeds you need tocontrol. It may take a combination of herbicides to control the various weeds in aplantation because no single one works best in all situations. For example, a chemicalmixture will work better than a single chemical when both grasses and broadleafplants are present. Dalapon will control the annual and perennial grasses; 2,4-D will

control the broadleaf plants. Applying a combination of postemergent herbicide andsimazine is often the most effective way to control weeds. The postemergent herbicidecontrols initial vegetation, and simazine provides residual weed control.

Applying chemicals-If your land is fairly level and the trees are uniformly spaced,you can use a farm-type sprayer to either broadcast the chemical or spray it in strips.Broadcast spraying covers the entire area and uses the most herbicide. Strip sprayingcosts less than broadcast spraying and reduces the possibility of soil erosion. Spray-ing 2-foot strips on each side of walnut seedlings at IO- or 12-foot spacings requiresonly 30 to 40 percent as much herbicide as broadcast spraying.

Spot spraying 4-foot circles around each tree, using a hand-held backpack sprayer, isthe the most versatile and, for smaller areas, probably the easiest and cheapest wayto control weeds.

Broadcast spraying generally requires more than 20 gallons of water and chemical tocover an acre. When spot or strip spraying, adjust the amount of solution per acre inproportion to the actual amount of ground sprayed. Monitor agitation, pressure, andcalibration carefully to ensure an accurate rate of application.

Herbicides-what, when, how much

Vegetation present. Apply postemergent herbicide in combination with simazine forresidual weed controlA. Walnut seedling absent:

1. Dowpon M (dalapon) 4-15 lbs/acre2. Dowpon M 4-15 lbs/acre

plus 2,4-D l-3 Ibs/acre3. Amitrol-T (amitrole) 2-4 Ibs or 1-2 gals/acre4. AAtrex (atrazine)’ 2%5 Ibs/acre5. Roundup (glyphosate) V / 2 - 2 qts/acre

B. Walnut seedlings present:1. Roundup (glyphosate) F/2-2 qts/acre

lApply atrazine in the fall preceding the spring when you plan to plant. Usually, anapplication of atrazine without simazine will provide sufficient weed control.

Precautions.-Before applying any herbicide, check State and federal regulations con-cerning its use, follow directions on the label, and take recommended safety precau-tions. Although the recommended chemicals are not normally considered dangerous,be sure to handle with care.

Felix Ponder, Jr.


Ground Cover Management

The ideal ground cover in a black walnut plantation would be similar to that in adense mature forest or mixed black walnut stand. Unfortunately, when a plantation isestablished, regardless of the type of site preparation, the walnut seedlings will not betall or dense enough to shade out the vegetation that competes against them. Mostplantations go through a natural succession from annual weeds to perennial weedsand then grasses if trees are widely spaced and free to grow.

Criteria for Choosinga Cover Crop

The type and amount of ground competition can greatly affect black walnut survivaland growth. In general, legumes increase tree growth if they persist; and grassesreduce growth. More testing is needed before we can make specific recommendationson ground cover; however, the following is a list of general criteria to consider whenselecting a cover crop for your plantation.

1. Ground cover should not compete strongly with your walnut.l does most of the vegetative growth occur during periods of walnut growth or

when soil moisture is inadequate?l does the ground cover produce phytotoxins-chemicals that will limit walnut

growth?2. Ground cover should be easy to establish and maintain on your site.

l are varieties available that are adapted to your section of the country?l is seed readily available at a reasonable cost?l will ground cover persist long enough to justify the cost of establishing it?l are shade-tolerant varieties available

3. Ground cover should produce adequate biomass to control other weeds.l can the ground cover overtop and smother existing herbaceous competition?l will the ground cover increase or decrease fire hazard in your plantation?

4. Ground cover should improve soil structure and/or fertility.l does the ground cover fix nitrogen and if so, how much annually?l will the ground cover result in rapid litter accumulation and increased organic

matter in the soil?5. Ground cover should be relatively free of pests, especially pests that may attack

walnut.

Your choice of ground cover is probably limited to those species used for hay,pastures, or green manure cropping. For silvicultural treatments, use half of theseeding rate suggested for agricultural uses unless site preparation is minimal. Con-tact your local extension agent for more information on how to establish the groundcover and how much of what varieties to plant. The agent knows about the soil typesin your area and what other landowners are growing. The following list describessome of the most common ground covers, their principal uses, seeding rate foragricultural use, rate of establishment, pattern of stem growth, longevity, and whethertested as a cover crop with black walnut or other hardwoods.

Species

Alfalfa foragepasture

R e d c l o v e r foragepasturegreen manure

Ladino orWhi te c lover

Tall fescue

pas turesb e e s

foragespas tures

Timothy foragespas tures

Birdsfoottrefoil

Crownvetch

ground coverpasture

ground coverforages

Alsike clover pas turesb e e s

S w e e t c l o v e r green manureforagesb e e s

Bromegrass foragespasture

Orchardgrass foragepasture

S e r i c e alespedeza

Annua llespedeza

ground coverforages

foragepasturegreen manure

Hairy vetch green manure

Cr imson c lover green manureforageb e e s

Principaluses___--.---...

Seedlingrate-______

(Ibs/acre)

10-20

Rate of Pattern of Longevity Tested’establishment stem growth

moderate erect perenn ia l NA

8-10 rapid erect short-livedperenn ia l

NA

2-4 moderate prostrate perenn ia l NA

2 0 - 3 5 rapid upright perenn ia l

5-10 moderate upright perenn ia l NA

5-10 moderate procumbent perennial 0

15-20 slow procumbent perennial t

4.5-8 moderate decumbent short-livedperenn ia l

NA

10-15 rapid upright b iennia l +



10-18 slow upright perenn ia l

15-25 rapid procumbent annual

4 0 - 4 5

15-20

rapid

rapid

t

t +

+ t

v ines a n n u a l

erect a n n u a l

(Tab le cont inued on next page)

(Table Cont inued)

Species Principaluses

Seedling Rate of Pattern of Longevity Trate establishment stem growth

K e n t u c k ybluegrass

Bermuda grass

Subter raneanclover

pasture 2 0 - 2 5

lbs/acre ground cover 60-70

Arrowleafclover

foragepastureb e e s

5 - 8

(lbs/acre)

pasture 15-25groundcover

ground cover 7-12pastureforage

oils 3 0 - 5 0green manure

slow upright perennial NA

rapid procumbent perennial NA

rapid

rapid

slow

rapid

upright annual t

p r o c u m b e n t a n n u a l t

v ines perennial NA

erect annual + t

---J N A = no data available; + = beneficial to some hardwoods; t + = beneficial to all hard-

woods tested; 0 = mixed results with hardwoods; and - = reduced growth on testedhardwoods.

J. W. Van Sambeek

3


Fertilization

Fertilization is perhaps the least understood of all the cultural practices associatedwith managing black walnut trees. Many fertilization studies have been done, but theresults have been inconsistent and hard to compare. So we are only able to makegeneral recommendations for fertilizing black walnut. However, first, there are somegeneral points to keep in mind.

Our best advice for ensuring good walnut growth is to locate your plantation on anideal site. Don’t fertilize walnut trees on good sites, especially young trees. Fertilizationdoesn’t seem to help the trees grow; but it does help weeds grow, which then sup-press walnut growth.

Fertilizing pole-size and larger trees is likely to provide the best economic return.Chemical analysis of walnut leaves can indicate current nutrient element levels of thetrees and suggest probable response to fertilization with nitrogen (N), phosphorus (P),potassium (K), and calcium (Ca) (table 1). Of these elements, N deficiencies are mostcommon; and use of N increases diameter the most. Height growth is seldom in-creased by fertilization. However, all four elements can be effective in improvinggrowth and nut production.

Table 1 .-Tentative critical foliar nutrient element levels- for diagnosing nutrient defi-ciencies in black walnut trees

Deficient (will Intermediate AdequateNutrient probably respond (may or may (will probablyelement to fertilization) not respond to not respond to

fertilization) fertilization)

________________________________________----- Percent ________________________________________-----N Below 2.00 2.00-2.60 Over 2.60P Below .10 .10- .25 Over .25K Below .75 .75-1.30 Over 1.30Ca Below .50 .50-1.10 Over 1.10

‘Based on analyses of mature leaves collected about mid-August (Phares and Finn 1971).

Before deciding to fertilize, determine if there are moisture or physical /imitations thatmay be affecting tree growth. Remember, fertilizer cannot compensate for these twolimiting factors,

If you do decide to fertilize, identify several trees to receive no fertilizers; use thesetrees to compare the growth of fertilized trees in terms of the amount of growth and

References

its duration, and to estimate when to refertilize. Do not refertilize if fertilized trees growno better than trees not fertilized. Refertilize when the satisfactory growth response tofertilizer is no longer evident when compared to trees not fertilized. All fertilized treesshould be free to grow or released before fertilizing.

For pole-size and larger trees managed for timber, apply 3 pounds of N per tree.Spread fertilizer evenly around the tree in late spring. Add 5 pounds of triple super-phosphate and 8 pounds of muriate of potash if trees are managed for timber andnuts. Except for Ca, treatments may need to be repeated every 3 to 5 years. Frequentfertilization, especially with N, can increase the need to add lime to maintain andraise pH. The pH range for growing black walnut is 5 to 8.

Losche, C. K. 1973. Black walnut growth better on deep, well-drained bottomland soils.Res. Note NC-154. St. Paul, MN: U.S. Department of Agriculture, Forest Service,North Central Forest Experiment Station. 3 p.

Maeglin, R. R.; Hallock H.; Freese, F.; McDonald, K. A. 1977. Effect of nitrogen fer-tilization on black walnut growth, log quality, and wood anatomy. Res. Pap.FPL-294. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Pro-ducts Laboratory. 13 p.

Phares, R. E.; Finn, R. F. 1972. Using foliage analysis to diagnose nutrient deficien-cies in black walnut. Northern Nut Growers Association Annual Report. 62(1971):98-104.

Ponder, F., Jr. 1980. Fertilization improves black walnut growth on a poorly drainedsite. Tree Planters Notes. 31(4): 17-19.

von Althen, F. W. 1976. Ten-year results of thinning and fertilizing of a pole-size blackwalnut plantation. Rep. O-X-245. Sault Ste. Marie, ON: Canadian Forestry Service,Great Lakes Forest Research Centre. 17 p.

Felix Ponder, Jr.


NOTESSome sites don’t have enough moisture to grow good black walnut trees. This isespecially a problem where drainage is excessive or where soil volume suitable forroot development is limited by soil depth or impermeable soil layers. Unless other fac-tors are limiting (and this is often the case), irrigating such sites may help to maintaintree growth during periods of inadequate precipitation and/or high evapotranspiration.But keep in mind: it probably won’t pay to irrigate just to increase the value of mer-chantable trees.

The moisture necessary for tree growth can come from rainfall, subsurface moisture,or irrigation. Normally, if well distributed, trees do well without supplemental water inareas where 30 inches or more of rainfall occurs. Of course, the amount and frequen-cy of rainfall required will depend on how much water the soil will hold.

On some sites, lack of available water is less of a problem than elsewhere becauseof “perched” water tables, where water is restricted from moving downward in the soillayer but, rather, collects in the rooting zone. In such cases, efforts to maintain anadequate supply of available water are overshadowed by the site’s poor quality. Asidefrom texture, which also influences the soil’s water holding capacity, both drainageand aeration affect tree growth and irrigation practice. A rise in the water tablereduces the amount of oxygen available to roots. Increasing the available water alsoincreases nutrient uptake, diminishing what may already be a limited supply in shallowsoils.

Irrigation methods include flood, furrow, border strip, sprinkler, drip, and trickle. Flood,furrow, and border strip methods use soil-constructed diversions and a small amountof hardware to deliver water by gravity to trees. Sprinkler, drip, and trickle irrigationsystems require more equipment and hardware to install and maintain.

If you decide to irrigate, you will need to estimate how much water to add. With flood,furrow, border strip, and sprinkler systems (also called surface irrigation methods), it isimportant to determine the amount of water the soil can hold, to prevent adding toomuch water and temporarily “waterlogging” the soil. For drip and trickle irrigation, thiscalculation is less important than for other methods because frequent, low-pressure ir-rigations continually replace water in the root zone as it is used.

The amount of water to apply during an irrigation can be determined with elaborateequipment. However, as a rule, trees need about 1 to 1% inches of rain per week.Calibrate your equipment to deliver this amount of water over 1 week. Depending onyour system, a watch and/or rain gauge may be all you will need. Dealers and sup-pliers of irrigation equipment are good sources of advice on determining water needsfor your soil. You can also contact the Soil Conservation Service or the State andPrivate Forestry branch of the Forest Service.

Felix Ponder, Jr. and F. Danny McBride


Interplanting nurse trees and shrubs with walnut trees can greatly improve walnutgrowth and quality (fig. 1). In addition, nurse crops have been used for estheticreasons; for wildlife food or cover; and for intermediate crops like Christmas trees,pulpwood, or fenceposts. But nurse crops should be selected carefully-not all areequally effective on every site.

Figure I.-Walnut interplantedwith autumn olive. Note the l a c kof a competing herbaceousunderstory in these plantings.

Most nurse crops we’ve tested have been nitrogen-fixers-they take nitrogen from theatmosphere and add it to the soil in a form available to other plants. Walnut trees usea lot of soil nitrogen, but many sites being planted to walnut are low in availablenitrogen.

The following nitrogen-fixing species have been tried in walnut interplanting.

Autumn olive, a multiple-stemmed, densely foliated shrub, has stimulatedwalnut growth on all but the best walnut sites. Unfortunately, the cultivar ofautumn olive originally planted as food and cover for wildlife is spread byseeds into uncultivated areas, and several States are discouraging thefuture planting of autumn olive.

Russian olive, a small, densely foliated tree, is a suitable alternative toautumn olive in the northern part of the walnut range. Russian olive canalso spread to uncultivated areas; it is prone to diseases that will limit itsgrowth.

European (Black) alder and black locust have stimulated the growth ofwalnut on some sites, but both can overtop and suppress walnut trees ifthey are not managed. Fortunately, both species are relatively short-livedbecause of locust borer damage on black locust and European alder’s sen-sitivity to juglone

Nurse crops can help walnut trees in other ways besides increasing the availability ofsoil nitrogen. They protect walnut trees from wind, moderate soil and air temperatures,improve soil texture, reduce the incidence and severity of foliar diseases, and reducecompetition from the understory. Of these benefits, reduced competition from theunderstory, especially grasses, may be the most important (see Note 2.06: GroundCover Management). Walnut trees alone will not produce enough shade to excludethe understory vegetation before tree competition reduces growth (see Notes 3.03:First Thinning and 3.04: Second Thinning). Interplanting other trees or shrubs withwalnut apparently helps maintain a high total crown cover without as much tree-to-treecompetition as in pure walnut plantations.

Only a few non-nitrogen-fixing trees or shrubs have been tested in walnut interplan-tings. Amur honeysuckle, a densely foliated shrub, is promising because it has agrowth rate and crown structure similar to autumn olive. Eastern white pine has beenencouraged because it can be harvested early in the walnut rotation for Christmastrees or later for pulpwood. Hardwood species such as white ash, red oak, and sugarmaple that have widespreading branches and dense foliage can provide thenecessary shade to suppress the competing understory vegetation.

The following table lists some possible species for interplanting with walnut, theirorigin, degree of shade tolerance, expected growth rates, mature height, ability to fixnitrogen, and major uses:

Common and Shade Growth Maturescientific name tolerance1 fate* height

Autumn olive M M-R 15-20(Elaeagnus umbellata)

Russian olive M-l M - R 25-30(Elaeagnus angustifolia

European alder I R 40-50(Alnus glutinosa)

Black locust I R 70-80(Robinia pseudoacacia)

Amur honeysuckle M M-R 15-20(Lonicera maacki)

Eastern white pine TM M 80-l 00(Pinus strobus)

Red oak M M-R 60-80(Quercus rubra)

White ash M M-R 70-90(Fraxinus americana)

Sugar maple T S-M 80-100(Acer saccharum)1T = shade tolerant, M = intermediate tolerance, I = intolerant.

Yes

Yes

Yes

Yes

N o

N o

N o

N o

N o

W,E

W,E

W,E,P

W,P

W,E

W,E,P,L

W,E,P,L

W,E,P,L

W,E,L

2 R = exceeds that of walnut, M = similar to walnut, S = slower than walnut.3 W = wildlife habitat, E = esthetic or screening, P = pulpwood or posts, L = forest prod-

ucts (lumber, veneer, gunstocks, millworks, etc.).

Fixes Majornitrogen uses3

J. W. Van Sambeek

3

Multicropping


NOTESMulticropping involves planting crops between wide-spaced rows of planted blackwalnut. Soybeans, winter wheat, and other crops can provide early financial returnsthat may help offset the cost of establishing a plantation and provide some incomethrough this phase. An additional advantage for some growers is that more of theland is used, increasing the yield per acre.

Obviously, the walnut grower’s first concern should be to produce veneer logs, timber,and possibly nuts. Consider the following points before planting other crops in yourwalnut plantation:

l Small plantations may not be large enough to economically accommodatemulticropping as an alternative to walnut alone.

l An ultimate spacing of 40 x 40 feet is desirable. However, this spacing provides foronly 27 trees per acre at the end of the rotation and eliminates the opportunity toselect crop trees early in the rotation. Therefore, an initial spacing of 10 feet bet-ween trees in the row, with rows 40 feet apart, is a good starting point.

l Multicropping does not eliminate the need for pruning, weed control, and good treegrowth (see Notes on these subjects elsewhere). In addition to the usual requiredpruning, branches may need to be removed to prevent them from interfering withthe operation of equipment. Walnut trees also benefit from fertilizer applied forplanted crops. Cultivation of the planted crop will help control weeds along therows of walnuts. Weeds within the row can be controlled by spraying Roundup’

The type of crops you plant will be determined by the growth rate of the trees. Walnuttrees will occupy more and more of the plantation area as they develop, decreasingyour multicropping options. Because most black walnut sites are also good soybeanand wheat sites, these three crops are logical companions. However, shading will pro-bably limit soybean production after 7 years. Winter wheat could possibly be plantedover a longer period because black walnut leafs out late. Both soybean and wheatyields will probably be a little smaller than under normal cropping systems.

Planting fescue for hay and grazing livestock could be another use for your plantationtowards midrotation. The number of cows or other grazing animals and the amount ofhay per acre depend on the site quality, growing conditions, and length of grazingperiod. It may be necessary to protect the walnut trees from animals.

Multicropped black walnut trees will probably produce commercial nut crops by age15, and many will produce nuts by age 10. Consistent nut crops could provide incomefor most of the remaining rotation period.

1Menfion of trade names does not constitute endorsement by the USDA ForestService.

References Ferrell, R. S.; Bentley, W. R . 1969. Plantation investment opportunities in black walnut.Journal of Forestry. 67: 250-254.

Garrett, H. E.; Kurtz, W. B. 1980. Black walnut multicropping management. WalnutCouncil Bulletin. 7: 15-19.

Felix Ponder; Jr.


Corrective Pruning

Young black walnut trees may fork or produce multiple leaders when their terminalshoots are damaged by frost, insects, animals, or humans. Because a walnut treemust develop a single, straight stem for valuable lumber or veneer, corrective pruningis often needed to remove lateral branches that compete with the terminal fordominance. But pruning can also cause a tree to grow more slowly by removing partof its food manufacturing plant, the crown.

Is Pruning Needed? Before you begin to prune, decide if it is really needed. Sometimes a delay in pruningmay eliminate the need for it. About one-third to one-half of the trees that developform problems will correct themselves within a year or two if they are growing well.Or, if your trees are spaced closely enough, a problem tree might have to be re-moved anyway in an early thinning. Corrective pruning is most likely to be needed inwide-spaced plantings (spacing of 20 feet x 20 feet or greater), because most of thetrees planted will be harvested for sawtimber or veneer.

How to Prune

Coppicing

If you decide to prune, remember that the objective is to produce trees with single,straight stems while minimizing the amount of leaf area removed so that the vigor ofthe tree is not reduced.

Corrective pruning should normally be considered during the first several years afterplanting, until the desired log length-generally 9 or 17 feet-has been reached.

If two or more leaders are competing for dominance, remove or cut back all but oneso that the selected leader can develop into the main stem. The selected leader neednot be perfectly straight and upright at the time of pruning. Removing the competingleaders will allow the selected one to straighten and grow upright after one or moregrowing seasons.

For trees that appear to be hopelessly deformed, you can use a severe form of cor-rective pruning called copping. In coppicing, the tree is cut completely off near theground. If trees are grafted seedlings, be sure to cut high enough above the graftunion so that new sprouts will be produced from the grafted stem and not from theroot stock. Coppicing should be done in the late dormant season or very early spring.Normally several sprouts will grow up from the stump. Identify the best of these bylate June or early July of the same year, and then cut off the other sprouts.

High Coppicing

References

A variation of coppicing, called high coppicing, has also been used for young walnuttrees. If a tree has 1 to several feet of straight stem below the hopeless deformity, cutoff the tree just below the deformed section, if the diameter of the stem at that pointis 2 inches or less. One or more sprouts should develop near the point of cutting.Return to the tree in late June or July to cut off all but the one best sprout.

In pruning, it’s not possible to prescribe a standard treatment; each tree must betreated individually. But keep in mind that the least amount of pruning necessary tocorrect the form problem will produce the best results.

Beineke, W. F. 1982. Corrective pruning of black walnut for timber form. FNR-76. WestLafayette, IN: Purdue University, Cooperative Extension Service. 7 p.

Bey, C. F. 1976. How to “train” black walnut seedlings. St. Paul, MN: U.S. Departmentof Agriculture, Forest Service, North Central Forest Experiment Station. 4 p.

Richard C. Schlesinger


Lateral Pruning

One thing that makes some walnut wood valuable is something it doesn't have:defects. But defect-free wood can be produced only after a branch has fallen off thetree or been removed. Black walnut trees do not prune themselves readily. Evensmall branches tend to leave stubs when they die, and large branches may hang onthe tree for many years after they die. So lateral branches must be pruned to producehigh-value, knot-free wood.

Pruning can begin once the trees are 10 to 12 feet tall, but should be confined to thelower half of the tree stem. Generally, pruning should leave at least half of the treestem with branches, and the leaf area should be reduced by no more than 25 per-cent in any one year.

Prune live branches during the latter part of the dormant season, but before the treesstart to grow in the spring. Pruning at this time of year minimizes the time that prun-ing wounds are open to infection. Dead branches can be pruned at any time, but donot cut into the branch collar that generally forms around dead branches. Doing sowill create a fresh wound.

Prune branches when they are small, generally less than 2 inches in diameterbecause small wounds are more likely to heal over without becoming infected. Also,pruning small branches is much easier than pruning large ones. However, if the treeis growing well, even fairly large wounds of 4 to 5 inches can heal successfully.

Continue to prune periodically until at least the first 9 feet of the tree is clear becauseveneer logs are normally 8 feet long. If you want a large crowned tree for nut produc-tion, stop pruning at 9 feet. If wood production is your primary concern, then continuepruning until at least 17 feet are clear so that two veneer logs can be produced.

Target pruning (fig. 1) is the best way to get the benefits of pruning while avoiding theproblems.

Several tools can be used for pruning. Generally, the pruning saw will produce thebest results. Long-handled pruners can be used on branches 1 inch in diameter orless. Pruning saws can be used on larger branches. When pruning above 9 feet,work from a ladder or use a pole saw. You can also use lightweight chain saws, butbe extremely careful to avoid damaging the tree or yourself.

Dead BranchI I

Living Branch

Branch Bark

Figure l.-Target pruning steps

1. Begin by locating the branch bark ridge.2. Find target A-outside of the branch bark ridge.3. Find target B-the swelling where the branch meets the

b r a n c h c o l l a r .4. if B is hard to find-drop a line at AX. The angle XAC is equal to the angle XAB.5 . If the branch to be pruned is large, first make a stub cut a few inches from the branch collar.6. Make the final cut at line AB.7. Caution: Do not cut behind the branch bark ridge or cut the branch collar, do not leave stubs, do not

paint cuts--except for cosmetics, and do not leave flat top when topping.

The time required to prune depends on the number and size of the branches re-moved and the equipment used. For 3- to 5-inch diameter trees that have never beenpruned, it takes about 3 minutes to prune six branches from the first 8 feet using ahand saw. It takes about 9 minutes to remove 13 branches from the first 18 feet ofsimilar trees.

Keep these two general principles in mind when pruning. (1) Removing live branchesremoves part of the food manufacturing capability of the tree, and thus can reducetree growth. (2) Disease organisms can enter the tree through pruning wounds ordead branches. You’ll need to take special care that wounds are as small as possible,that healing is promoted, and that tree growth is maintained. If done carefully andcorrectly, pruning can greatly increase the value of the trees. If done carelessly, it cando more harm than good.


First Thinning


NOTESThinning is one of the most important silvicultural practices available to tree growers.It is particularly important with black walnut because walnut trees differ widely invalue, depending on their quality and size. Thinning a walnut stand can greatly in-crease its value by making all the moisture, nutrients, and light available to a fewhigh-quality trees and by removing the low-quality trees.

Deciding when and how much to thin requires some care. Thinning too late allowsbetween-tree competition to slow the growth of the better trees. Thinning too sooneliminates insurance trees, makes the choice of crop trees less certain, and reducesthe potential benefits of limited competition in restricting the growth of lower branches.So, thinning often involves compromises.

1. When to Thin? A useful measure for evaluating the need for thinning is crown competition factor(CCF). For plantations with a regular square spacing, CCF can be easily determined ifthe size of the plantation, approximate number of trees, and average d.b.h. in inchesare known, using the following equation.

(total # trees)(3.14)(0.997 d.b.h. + 2 .436CCF = ~~

44,000 (# acres)

The following table gives the average diameter for CCF’s of 100 to 150 for severalcommon spacings.

Tree diameter at which to thin(In inches)

CCF 5x10

Original spacing (feet)

8x12 10x10 11x11 12x12 15x15

100 1.6 3 . 1 3.2 3.8 4.3 6.0110 1.8 3.4 3.5 4 . 1 4.7 6.5120 1.9 3.6 3.7 4.4 5.0 6.9130 2.1 3.9 4.0 4.7 5.3 7.2140 2.3 4.1 4.3 4.9 5.6 7.6150 2.5 4.3 4.5 5.2 5.9 8.0

If you want to maintain maximum growth rate of your crop trees, thin when CCF is100. For each additional 10 CCF units above 100, expect the growth rate to go downby 4 to 5 percent per year. For example, if the diameter growth rate were 0.4 inchesper year at a CCF of 100, it would be 0.3 inches per year at a CCF of 150, a25-percent reduction.

For plantations with a wider spacing between rows than within rows, thin when theaverage tree crown width (CW) within a row is 1.5 to 2 times the distance betweenthe trees, using the following equation:

CW(feet) = 1.993 d.b.h.(inches) + 4.873

2. How Much to Thin? Heavy thinning provides plenty of growing space for the crop trees and delays thenext thinning. However, the open stand conditions after thinning may encourage thegrowth of grasses, weeds, or invading trees. Light thinning may not provide enoughadditional growing space for each crop tree, but it does allow you to retain more in-surance trees. It also provides more side shade that may slow the growth of sidebranches on the crop trees.

3. Which Trees Should Examine small groups of trees within the planting. If the spacing is much closerBe Left After Thinning? within the rows than between them, as in a 5- x lo-foot planting, choose the better

tree from groups of two trees within the rows. If a tree has died or is missing, theother tree of the “pair” automatically becomes the tree to keep.

In more regularly spaced plantings, such as 10- x lo-foot, examine groups of 16 (ifhalf of the trees are to be left) or 9 (if two-thirds of the trees are to be left). From asquare four trees by four trees, select the best eight to leave, again considering anymissing or dead trees as part of the group to remove. From the nine-tree group, asquare of three trees by three trees, select the best six. Mark the selected trees bytying a colored plastic ribbon around each at eye level.

Once you’ve marked all the groups, reexamine the entire stand, looking for areaswhere too many or too few trees will be left. As a general rule, each tree to be leftshould benefit from the thinning by the removal of at least one of its nearestneighbors. Also, the thinning should not result in large, open areas unoccupied bytrees.

Finally, thin carefully to avoid mechanical damage to the trees that are left. Also,avoid chemical thinning (timber stand improvement) or chemical treatment of cutstumps because chemicals may spread from treated trees to the trees that are left.

Reference Anonymous. 1981. Quick reference for thinning black walnut. St. Paul, MN: U.S.Department of Agriculture, Forest Service, North Central Forest Experiment Stationand Northeastern Area State & Private Forestry. 32 p.



Second Thinning

Thinning your black walnut stand the second time is much like thinning it the firsttime except that you face tougher decisions about which trees to keep (see Note 3.03:First Thinning). Most of the poorest trees have already been removed.

Deciding when and how much to thin is still important. Delaying thinning allowsbetween-tree competition to slow the growth of the better trees. The amount of woodproduced per year on an acre of land is about the same no matter how many treesthere are. So, if there are many trees, each will grow only a little; if there are fewtrees, each individual tree can grow much more.

The following tables give the average diameter for stocking (crown competition factor)levels of 100 to 150 for several common planting spacings in two stands previouslythinned by different amounts.

Table I.-Tree diameter at which to make a second thinning in a stand previouslythinned to two-thirds of its original size

(In inches)

C C F 5x10

100 2.5110 2.7120 2.9130 3.1140 3.4150 3.6


8x12 10x10 11x11 12x12 15x15

4.3 4.5 5.2 5.9 8.04.7 4.8 5.6 6.3 8.55.0 5 . 1 5.9 6.7 9.05.3 5.4 6.2 7.0 9.45.6 5.7 6.6 7.4 9.95.9 6.0 6.9 7.7 10.3

Reference

Table 2.-Tree diameter at which to make a second thinning in a stand thinned tohalf its original size

(In inches)

C C F 5x10


8x12 10x10 11x11 12x12 15x15

100 3.2 5.4 5.6 6.4 7.1 9.6110 3.5 5.8 5.9 6.8 7.6 10.1120 3.7 6 . 1 6.3 7.2 8 . 1 10.7130 4.0 6.5 6.7 7.6 8.5 11.2140 4.3 6.8 7.0 8.0 8.9 11.7150 4.5 7.2 7.4 8.3 9.3 12.2

For the second thinning, you’ll need to make the same three decisions as for the firstthinning: when to thin, how much to thin, and which trees to leave (see Note 3.03:First Thinning).

When selecting which trees to keep in the second thinning, be sure to consider thedistance between any two crop trees. Generally, the minimum distance between anytwo crop trees should be 55 percent of the sum of their crown radii. For example, thecrown radii of a 7-inch-diameter tree and an 8-inch-diameter tree would be 9.4 feetand 10.4 feet, respectively. To find the crown radius in feet, multiply the diameter in in-ches times 0.997 and add 2.44 feet. The two trees should be at least 10.9 feet apart(9.4 plus 10.4 times 0.55) if both are to be retained as crop trees.

Once you’ve marked all the groups, reexamine the entire stand, looking for areaswhere too many or too few trees will be left. As a general rule, each remaining treeshould benefit from the thinning by the removal of at least one of its nearestneighbors. Also, the thinning should not result in large, open areas unoccupied bytrees.

Finally, thin carefully to avoid mechanical damage to the trees that are left. This isespecially important in the second thinning because the trees removed are largerthan in the first thinning, and there are fewer insurance trees. Also, avoid chemicalthinning (timber stand improvement) or chemical treatment of cut stumps becausechemicals may spread from treated trees to the remaining trees.

Anonymous. 1981. Quick reference for thinning black walnut. St. Paul, MN: U.S.Department of Agriculture, Forest Service, North Central Forest Experiment Stationand Northeastern Area State & Private Forestry. 32 p.



Releasing Walnut in Natural Stands

Black walnut trees generally grow singly or in clumps in natural stands. To make themost of their potential value, you’ll need to give these trees some “elbow room” fromnearby trees and vegetation that compete with them for moisture, nutrients, and grow-ing space. For individual trees in natural stands, release is the most important andworthwhile silvicultural treatment you can apply.

When to Release Some type of release may be needed in these three cases:

1. Young trees growing in forest openings. Release by controlling weeds (see Note2.05: Weed Control). Cut or kill any brush or other small trees that overtop thewalnuts. If there are many young trees in the opening, so that the area will bemanaged for walnut, enlarge the opening to at least one-half acre to provideenough light.

2. Vines growing around individual trees. Several types of vines may be present, butwild grapes are the most damaging. The vines can deform the trees and kill themif left alone. Release by severing the vines and treating the cut ends carefully witha herbicide.

3. Trees of all sizes that are competing with other trees for light, moisture, andnutrients. In this situation, release and thinning have the same purpose; butrelease focuses on an individual tree’s need for growing space rather than on thestand of trees.

A walnut tree will grow much more slowly in diameter if it’s crowded. You canestimate how seriously crowded an individual tree is by comparing the tree’s actualcrown width with its potential crown width. An easy way to approximate potentialcrown width in the field is by estimating (or measuring) the d.b.h., doubling it, and ad-ding 5. Or, use this equation:

Crown width (feet) = 1.993 d.b.h. (inches) + 4.873.

Once you’ve determined the potential crown width, the next step is to estimate (ormeasure) the actual crown width. Then express the two widths as a ratio (ActualCrown Width/Predicted Crown Width). For example, a lo-inch-diameter tree mighthave an actual crown width of 19.8 feet and a predicted crown width of 24.8 feet. Thecrown width ratio would be 0.8, and the crown area would be 84 percent as large asif the tree were free to grow (table 1). More importantly, the tree’s diameter growthwould be about 25 percent less than if it were free to grow.

Table 1.-Estimating the effects of crowding

Crown widthratio

Maximum Potentialcrown area growth

-_-___________________ Percent ______________________

1 .oo 100 100.95 90 95.90 81 90.85 72 84.80 64 75.75 56 66.70 49 53.65 42 38.60 36 19.55 30 0

Although walnut trees are very sensitive to crowding, they respond well to releasefrom crowding. If all the walnuts in a stand are about the same age, the largest treesand those with the largest crowns will respond best. Release is best done when thetrees are still young and before they have been crowded too long.

For release, forest trees are often separated into four crown classes: dominant (withcrowns in the uppermost layers of the canopy), codominant (with crowns in the uppercanopy, but less free to grow than dominant trees), intermediate (with crowns slightlybelow the upper canopy, but receiving some light from above), and suppressed (withcrowns below the upper canopy and completely shaded). Even though walnut trees ofmany sizes, ages, and degrees of crowding have responded well to release, the bestcandidates for this treatment are from the dominant, codominant, and intermediateclasses.

To be effective, release should increase the growing space available to the tree on atleast three sides. As a general rule, there should be at least 10 feet between thewalnut crown and any adjacent tree crowns after release. Additional treatments will berequired periodically as the walnut crown grows out into available space.

Felix Ponder; Jr. and Richard C. Schlesinger


Revitalizing Stagnating Stands

Has your plantation or natural stand of black walnut trees stopped growing rapidlyenough in height and/or diameter to meet your objectives? As a rule of thumb, walnuttrees should grow at least 1.5 feet in height each year during the early part of therotation and 0.3 inches in diameter during the latter part in short-rotation forestry.

Are the leaves of your trees smaller than normal (usually less than 12 inches long)?Do they turn yellow in late June and early July? If so, your stand may be stagnating;and the first step in revitalizing it is to look for the cause.

Why Stands Stagnate Several factors could be involved:

l The plantation or natural stand could be growing on soil unsuitable for walnut (seeNote 2.01: Choosing a Good Walnut Site).

l The trees may be too crowded (see Notes 3.03: First Thinning and 3.04: SecondThinning) or overpruned (see Notes 3.01: Corrective Pruning and 3.02: LateralPruning).

l The ground vegetation may be taking away too much of the moisture and nutrientsthe trees need for growth.

Tree growth depends on light, water, nutrients, carbon dioxide, and oxygen. If thetrees are overtopped by other trees or vegetation, they may not get enough sunlightand carbon dioxide. If they’re in inadequately aerated soil without enough oxygen,their roots may grow poorly.

Trees may not get enough nutrients and moisture if they have to compete directly withthe understory vegetation. They may also have to compete indirectly with other typesof vegetation that produce chemicals that reduce the trees’ ability to extract moistureand nutrients from the soil. Possible examples of this vegetation are: tall fescue,quack grass, goldenrod, asters, and ferns. Less than optimum walnut sites are morelikely to have inadequate supplies of nutrients and moisture for both trees andvegetation.

Three Ways to If the ground vegetation seems to be causing the stagnation, here are three ways toRevitalize Your Stand put some life back into your stand:

1. Control the vegetation with herbicides or with mechanical cultivation.. Weed controlis essential during the first 2 to 3 years after planting (see Note 2.05: Weed Con-trol). However, even after the trees are taller than the weeds, they apparently donot produce dense enough shade to dominate the site. So, chemical or mechanicalcontrol of the ground vegetation may also be needed in later years to increase thenutrients and moisture available to the trees.

On some sites, removing the ground vegetation may temporarily stimulate treegrowth while nutrients, especially nitrogen, are released from the decaying vegeta-tion. Available nitrogen is often low in stagnating stands. Premature yellowing of theleaves is one sign of this. If foliar nitrogen content is more than 2.5 percent, ade-quate soil nitrogen is available. If it’s less than 2.5 percent, fertilization may benecessary along with continuous weed control (see Notes 2.07: Fertilization and2.06: Ground Cover Management).

2. Plant nurse or companion trees or shrubs with the walnut trees (see Note 2.09: In-terplantings). Autumn olive has been particularly effective in increasing soil nitrogenthrough fixation, altering the types of understory vegetation, increasing wind protec-tion, and reducing the incidence of leaf diseases. Russian olive, European alder,and black locust (all nitrogen fixers) and white pine (not a nitrogen fixer) also ap-pear to be potential nurse trees.

3. Replace the existing understory vegetation with one that is compatible with walnuttrees (see Note 2.06: Ground Cover Management). Hairy vetch (an annual legume),crownvetch, and sericea lespedeza (perennial legumes) appear to be good choices.

Consider the following management questions before attempting to revitalize astagnating stand. Will the trees continue to grow slowly or just persist and eventuallydie if nothing is done? If you do remove the understory vegetation, are you likely toimprove growth enough to offset the additional costs? If the trees will continue to growslowly and you decide to do nothing, are you willing to accept the lower quality logsthat will be produced in a longer time? Is it time to place less emphasis on timberand more on nuts from your stand? If the trees will eventually die if you do nothing,you must decide between growing and not growing walnut trees. In either case, con-sider the consequences.

J. W. Van Sambeek and R. C. Schlesinger


Nut production

Spacing

Pruning

Managing GroundCover

Tending the Trees

Managing walnut trees for both nuts and timber might bring in extra profits, butthere’s a hitch. Maximizing timber yield conflicts with maximizing nut yields. So, toproduce both, growers need to compromise on spacing, thinning, pruning, andmanaging ground covers.

Initial tree spacing for nuts and timber should be 15 to 20 feet square. Planting at thecloser spacing of 10- to 12-feet square recommended for timber requires a thinningbefore you can adequately assess the nut production of individual trees. The crowncompetition factor (CCF) determines when to thin (see Note 3.03: First Thinning and3.04: Second Thinning). Significant competition among trees begins with CCF’s be-tween 80 and 100; therefore, a CCF between 70 and 90 is usually recommended fornut and timber production.

Nut production requires open-grown trees with large crowns; therefore, most growersprune walnut to produce one high-quality veneer log. Begin pruning side brancheswhen the trees are 5 to 10 feet tall; continue pruning off a few additional branchesannually until at least 9 feet of clear stemwood is obtained. The clear stem lengthshould never exceed 50 percent of the total tree height. Excessive pruning reducestree growth, increases internal wood defects, and results in epicormic sprouts.

After a 9-foot clear stem has been produced, continue spot pruning to create a scaf-fold branching system. Walnut tends to produce a whorl of branches at the base ofeach year’s terminal growth. Within each whorl, select two or three branches thathave the widest stem-to-branch angle, are evenly spaced about the central bole, andhave branch bark ridges without included bark (see Note 3.01: Corrective Pruning and3.02: Lateral Pruning). A strong scaffold branching system above the clear bole willmean fewer broken branches and higher nut yields in the long run.

The amount and type of ground cover can significantly affect walnut growth and nutyields. Cover crops will delay a tree’s bud burst and flowering, allowing more of theflowers to escape damage from late spring frosts. Legume cover crops are usuallyrecommended because they can provide part or all of the nitrogen walnut trees need.Do not plant grass cover crops; they are too competitive and can produce chemicalsthat inhibit walnut growth.

Walnut trees should begin producing nuts regularly on a good site when they are 8 to10 years old or 15 to 25 feet tall. Nut yield tables for plantation-grown trees are notyet available. Many black walnut trees may bear only irregularly or during alternateyears, but you can select those trees that regularly bear when you thin the plantation.One way to record nut production each year is by spraying a spot of paint on eachtree with a nut crop. Use a different color each year. When thinning the plantation,you can then rapidly evaluate each tree both for its stem size and quality and for itsnut production.

Several cultural factors can influence flower production, fruit set, and fruit maturation.Because female flowers are formed within the dormant buds when the current year’snuts are rapidly enlarging and filling, the immature flowers must compete with thenuts for carbohydrates produced by the leaves. Cultural practices such as fertilizationor thinning that increase the leaf surface area or sunlight striking the leaves shouldincrease the number of new flowers formed in the buds. To provide the nitrogenneeded for good fruit set, walnut plantations should be fertilized according to theircropping potential. For every 100 pounds of freshly husked nuts harvested, approx-imately 15 pounds of nitrogen must be added either through nitrogen-based fertilizersor legume cover crops.

Moisture stress, especially during July and August when the nuts are rapidly enlargingand filling, will drastically reduce nut production and quality. Be sure that your treesget the moisture they need (see Note 2.08: Irrigation).

Handling the Nuts Walnut trees generally drop their fruit in four phases:

1. shortly after flowering, because of natural pollination failures.2. summer, in response to damage by the walnut curculio.3. late summer, when incompletely filled nuts fall because of foliar diseases or

moisture stress.4. early autumn, mature nuts fall to the ground.

A bushel of freshly collected nuts weighs about 48 pounds and contains about 375nuts. To keep the nuts from overheating and losing kernel quality, spread freshly col-lected nuts out in shallow piles until husked. Wear rubber gloves when handling nutsbecause the hulls contain chemicals that can irritate and blister the skin. Husked nutscan be stored in open mesh bags and allowed to air dry. Nuts to be used for seedmust be kept moist and prepared for stratification (see Note 2.03: Direct Seeding).Nuts are usually purchased on a green hulled weight basis by local agri-businessfirms who are supplied with walnut hullers by walnut processors. After husking, aboutone-third of a bushel of nuts weighing 18 pounds will remain.

Evaluating the Nuts When managing a plantation for nuts and timber, you should evaluate the nuts fromsome of your best trees. Trees that consistently produce nuts with more than 4 gramsof kernel, kernel percentages higher than 20 percent with more than 50 percent ofkernel extracted as quarters, and fewer than 20 percent blind nuts are worth furtherevaluation and possible propagation as new cultivars for timber and nut production.

J. W. Van Sambeek

Walnut Anthracnose


NOTESWalnut anthiacnose is the most common leaf disease of black walnut. Caused by afungus, this disease makes walnut trees lose their leaves prematurely. This prematuredefoliation slows the trees’ growth and reduces the quantity and quality of nut crops.Wet weather in which the foliage is covered with moisture for prolonged periodsmakes the disease more severe.

Dark spots first appear on the leaf blades and petioles in spring as the leaves ap-proach their mature size (fig. 1). The spots may range from a few mm to around one-half inch in diameter. As the season progresses, more spots appear. Eventually, af-fected leaflets drop prematurely.

Control

Figure 1.-Walnut anthracnose leaf spots.

Control may not be required where trees are being grown exclusively for timber andwhere disease does not appear each year. But control measures may be neededwhere trees are being grown for a nut crop or where the site has a history of annualanthracnose epidemics.

References

Cultural.-Interplant walnut with autumn-olive or Russian olive. The olives interfere withspread of the disease spores from tree to tree, and olive leaves cover fallen infectedwalnut leaves on the ground. The olives also fix nitrogen in the soil. This helps createa more favorable nitrogen balance in the walnut leaves that makes them more resis-tant to infection. Nitrogen fertilization of young plantations also suppresses anthrac-nose infestations.

Chemical.-Apply the fungicide benomyl as a foliar spray, beginning in mid-June.Repeat every 3 weeks. At least four applications may be required for control.

Berry, Frederick H. 1981. Walnut anthracnose. Forest Insect & Disease Leafl. 85.Washington, DC: U.S. Department of Agriculture, Forest Service. 3 p.

Black, W. M.; Neely, Dan; Matteoni, James A. 1977. How to identify and control leafspot diseases of black walnut. St. Paul, MN: U.S. Department of Agriculture, ForestService, North Central Forest Experiment Station. 6 p.

Kenneth J. Kessler. Jr.


Mycosphaerella Leaf Spot

Mycosphaerella leaf spot causes premature defoliation of black walnut, which slowsthe trees’ growth and reduces the quantity or quality of nut crops (fig. 1). Thisdisease, caused by a fungus, has been found in North Carolina, Georgia, Illinois, andIowa. It is especially common in young black walnut plantations. Wet weather in whichthe foliage is covered with moisture for prolonged periods makes the disease moresevere.

Figure I.-Typical Mycosphaerella leaf spot lesions.

Small, angular-sided dark spots up to 4 mm in diameter first appear on leaf blades inspring as the leaves approach their mature size. As the season progresses, morespots appear-often concentrated at the tips or along the major veins of the leaflets.Eventually, affected leaflets drop prematurely.

Control

Reference

Control may not be required where trees are being grown exclusively for timber andwhere disease does not appear each year. But control measures may be neededwhere trees are being grown for a nut crop or where the site has a history of annualMycosphaerella epidemics.

Cultural.-Interplant walnut with autumn-olive or Russian olive. The olives interfere withspread of the disease spores from tree to tree, and olive leaves cover fallen infectedwalnut leaves on the ground.

Chemical.-Apply the fungicide benomyl as a foliar spray, beginning in mid-June.Repeat every 3 weeks. At least four applications may be required for control.

Kessler, Kenneth J., Jr.; Swanson, Linda B. H. 1985. How to identify and control blackwalnut Mycosphaerella leaf spot. HT-65. St. Paul, MN: U.S. Department ofAgriculture, Forest Service, North Central Forest Experiment Station. 6 p.

Kenneth J. Kessler; Jr.

Canker Disease

Most cankers in black walnut are caused by fungi that enter the tree through un-protected wounds, small injuries, or leaf scars. Cankers may damage trees by allowingdecay-causing organisms to enter the tree, by degrading the wood, and by weakeningor girdling the stem. They can be either annual or perennial, depending on how longthe canker-causing fungus operates.

Annual cankers, active for one season only, generally affect young, smooth-barkedwalnut trees. They often occur near the ground on the stem. The tree may developbasal sprouts below the canker, particularly if one-half or more of the stem has beengirdled by the canker (fig. 1). Annual cankers affecting less than one-fourth of thestem often heal, but affected trees may later develop weak seams at the former

Annual Cankers

canker locations.


Figure l.-Girdling annual canker on black Figure 2.-Two open-faced perennial Nectriawalnut. Note basal sprouts. cankers.

Perennial Cankers Perennial cankers caused by a Nectria fungus, are much more destructive than an-nual cankers (fig. 2). Nectria cankers may remain active for many years. In responseto the Nectria infection, the tree creates folds of callus at the canker site. After a few

Control

years, the canker begins to look like an open, target-like face. Nectria cankers, in ad-dition to creating a wood defect, weaken stems and make them susceptible to windbreakage.

Annual cankers.-If stems are girdled and sprouting occurs, remove girdled stem andall sprouts but the most vigorous one. Burn or remove all dead stems from the area.

Perennial cankers.-Nectria cankers usually develop around old branch stubs on thestem. In areas with a high incidence of Nectria cankers, prune lower branches toremove this source of infection. Encourage vigorous tree growth so that wounds willheal quickly. Release trees as required to prevent stagnation.

Kenneth J. Kessler, Jr.


Walnut Caterpillars and Other Defoliators

Walnut caterpillar

Leaf defoliators eat the leaves of trees and other plants, sometimes the leaves of en-tire trees. Defoliating insects usually do not kill trees by their feeding, but trees maylose their vigor and grow more slowly when attacked by many insects or whendefoliated several years in a row. Several types of leaf defoliators strike black walnut.

The most common one is the walnut caterpillar, which occurs throughout the easternUnited States. Walnut caterpillars are often found in masses on the trunk or feedingon the leaves (fig. 1). One colony can quickly defoliate an entire young tree. A veryyoung caterpillar is red and covered with grayish white hairs. A full-grown caterpillar isas long as 2 inches and has a black body with yellow stripes along each side. Theentire body is covered with long white hairs.

:

Fall Webworm The fall webworm is another common and conspicuous defoliator of walnut and othertrees throughout the eatern United States. It is easily recognized by its web, whichencloses one or more branches of a tree and sometimes an entire small tree (fig. 2).Webs begin appearing on the outer tips of branches about mid-July. As the summerprogresses, the webs enlarge and become more noticeable. The larvae live inside theweb, sometimes as many as several hundred to a colony. A full-grown larva is usuallypale yellow or green with a broad dark stripe down the entire back and a yellowstripe down each side. The body is covered with l-inch-long gray or red hairs.

Figure 2.-Fall webworm.

Grasshoppers andMay Beet les

Other insects besides caterpillars also feed on and defoliate walnut trees. Two ofthese include grasshoppers and May beetles. Grasshoppers may become a problemin young walnut plantations next to open fields that are mowed or cut periodically toproduce hay. The grasshoppers may move to the walnut trees after the field crop hasbeen cut. May beetles, also known as June bugs, feed on newly expanding buds andleaflets (fig. 3). The beetles also chew holes in already expanded leaves, causing ashot-hole effect in young leaves in early spring.

Control

Reference

F i g u r e 3.-May b e e t l e .

The simplest control method is to remove webbing and caterpillars by hand when youfirst notice them. This is less expensive and less environmentally damaging thanchemical control methods, particularly when only a few trees are affected. Repeateddefoliation over several years, however, may require chemical control. Usually no con-trol is necessary for May beetles. Consult your local extension agent for other recom-mended controls.

Farris, Marion; Appleby, James E. 1978. How to identify and control the walnut cater-pillar. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North CentralForest Experiment Station. 4 p.

Barbara C. Weber

Twig and Stem Borers


NOTESAlthough many twig- and stem-boring insects can be found in walnut trees, they aregenerally not a major problem for walnut growers. The two stem-boring insects thatcause the most concern and some damage are walnut shoot moths and ambrosiabeetles. Both cause multiple forks or crooks in the main stem of young trees, therebyreducing the potential for the mature trees to produce veneer or high quality lumber.

Walnut Shoot Moths Female walnut shoot moths lay their eggs in late summer on the undersides ofleaflets. Newly hatched larvae feed briefly and move to the base of a terminal bud tospin overwintering protective cases. In early spring the larvae leave their overwinteringcase and begin feeding on expanding buds. A small pile of excrement and webbingcan be found on damaged buds as the larvae tunnel into the bud. As the larvaegrow, they tunnel down the expanding shoot. The dying shoots frequently look as ifthey have suffered frost damage. In April or May, the mature larvae emerge, drop tothe ground, pupate, and then emerge as adults in late summer to start the cycle overagain.

Destruction of the terminal bud results in one or more new terminal shoots fromlateral buds below the damaged terminal (fig. 1). Many young walnut trees straightennaturally by producing a single dominant leader from one of these new terminalshoots. However, when such damage occurs annually, the trees may become badlydeformed with numerous forks and crooks (fig. 2). The trees may then require bothcorrective and side-branch pruning to produce straight, high quality stems.

Figure l.-New terminalfrom lateral buds belowd a m a g e d t e r m i n a l b u d .

shootst h e

Ambrosia Beetles

Figure 2.-Walnut trees Ib a d l yd e f o r m e d a f t e r r e p e a t e d a n n u a ldamage by walnut shoot mo ths .

Shoot moths also feed on older walnut trees. However, after a tree has developed astraight, single stem at least 9, 17, or 25 feet long (depending on your managementobjectives), forking within the crown will not reduce the tree’s value.

Adult females emerge in early spring from trees infested the previous year and flyshort distances to new host trees to excavate galleries and lay their eggs (fig. 3). Thelarvae feed on fungi growing in the gallery, pupate, and emerge as adults in about amonth to repeat the cycle. Two or more generations may occur each year, but theearly spring generation often does the greatest damage.

Figure 3.-Adult female ambrosiab e e t l e s e x c a v a t e g a l l e r i e s i n h o s ttrees and lay their eggs there.

Signs and symptoms of ambrosia beetle attack include pinholes, wilting leaves, stemdieback, and basal sprouts. Pinholes (fig. 4) are the entrance holes made by adultfemales as they attack the lower stem of trees. Pinholes are approximately 1/32 inchin diameter and are difficult to find except in the spring when sap flows from them.As the adult female excavates the gallery, she introduces a fungus into the wood thatoften causes wilting of the leaves and stem dieback, the most easily detected symp-tom of attack. Most ambrosia beetle-infested walnut trees produce basal sprouts thatcan rapidly replace the original stem (fig. 5). Resprouted trees are rarely attacked asecond time by ambrosia beetles.

Figure 4.-Pinholes made byadult females as they attack thel o w e r s t e m .

Figure 5.-Basal sprouts pro-duced by an ambrosia beetle-infested tree can rapidly replacet h e o r i g i n a l s t e m .

Summary

Ambrosia beetles usually attack the slower growing trees less than 10 feet tall in aplanting. When you find signs of attacks, remove and destroy dying stems as soon aspossible to reduce the beetle population in your planting. During the dormant season,prune away all but the largest basal sprout. Because basal sprouts grow rapidly inthe beginning, long-term height and diameter growth of the walnut trees will not begreatly affected.

Direct chemical control of the ambrosia beetle is impractical and not recommended.

Although stem-boring insects can cause damage, don’t panic if you find them in yourplanting. The initial damage they cause looks much worse than what the long-termdamage actually is. Some trees will recover fully by themselves, and you can helpmost others to recover by following the suggestions above.

J. W. Van Sambeek and R. C. Schlesinger

Deer


Preventing Animal Damage

Squirrels

No matter how carefully you tend your black walnut trees, you still have to contendwith animals that chew, gnaw, rub, break, or drill holes into the trees. Such damagemay cause black walnuts-particularly seedlings and saplings-to grow slowly, fork,and even die. Below are the most common and the most destructive animals in blackwalnut stands and what you can do to keep them from damaging your trees.

Buck deer rub against young black walnut trees in the fall to remove the velvet fromtheir antlers, often shredding the bark and leaving it hanging in strips. Larger treesare usually not affected. Deer may also nip the buds of seedlings, causing the mainstems to fork. Tree growth may be stunted in areas of large deer populations becauseterminal buds are eaten by the deer every year.

Control:

l Surround the plantation with a 5-wire electric fence 60 inches high or an 8-foot-highwoven wire fence (most effective, but most expensive method).

l Spray chemical deer repellent on trees. These repellents, however, are water solu-ble and must be reapplied after each rain.

l Hang deodorant bath soap or cloth bags containing tankage (dead animals thathave been dried and ground) on every second or third tree around the perimeter ofthe plantation (least expensive, but probably least effective method).

l Interplant more desirable shrubs for browsing, such as autumn-olive.

Squirrels feed on walnuts while the nuts are still hanging on the tree in late summerand after they have fallen in the fall. Squirrels also dig up planted walnuts, sometimeseven after the nuts have germinated. They locate buried seeds by smell and havebeen known to remove all seeds from some plantings.

Control:

l Place a generous portion of fresh cow manure on each nut to mask the odor com-ing from the nut. This is the cheapest and most effective squirrel repellent.

l Locate plantings at least 300 feet from standing timber because squirrels are reluc-tant to cross open spaces. If possible, delay planting until spring when alternativefood sources are available.

l Cover seeds with mechanical barriers such as hardware cloth, wire cones, orburnt, punctured tin cans (fig. 1).

Figure 1.-Mechanical barriers (clockwise from upper left), such as l-foot squares of hardware cloth an-chored with wire pins, cones cut from l-foot circles of hardware cloth, or punctured tin cans can preventsquirrels and other rodents from pilfering seed.

Hardware cloth.-A piece of coarse hardware cloth or chicken wire about 12 incheslarger than the seed spot will generally protect the seed and allow the seedling togrow through the wire. Use metal pins made from #9 galvanized wire to hold downthe corners. The hardware cloth or chicken wire should be removed in the fall afterthe seedling sheds its leaves.

Tin cans.-Place tin cans in a fire to remove the tin coating (so they will rust anddisintegrate). Cut out one end of each can and make an x-cut in the other end. Pryup the four points to make a l-inch opening. Hold the can open end up and add 1inch of soil. Drop in a nut and pack can full of soil. Place in planting hole with openend down and cover with an inch or two of soil.

Wire cones.-Cut two 12-inch-diameter semicircles from a 12-inch-square piece ofhardware cloth. Roll each into a cone and fasten with small pieces of wire leaving aone inch hole at the top.

Mechanical barriers are effective but time-consuming and expensive to prepare andput into place.

Other Rodents

Birds

Mice, rabbits, and other small mammals gnaw on the stems of young trees, usuallyduring winter, and remove patches of bark. Their teeth marks are usually visible at thebase of the tree.

Control.-Put wire screening around the base of young walnut trees. Mow the planta-tion in the fall and place tall poles throughout the planting as rests for predatory birds.

Sometimes birds break the main stems or branches of young black walnut trees byperching on them. The broken main stem or branches usually remain hanging on thetree. Red-wing blackbirds and owls are the most common culprits. Yellow-breastedsapsuckers also damage black walnut trees by drilling holes in the tree and feedingdirectly on the sap. The sapsucker may drill test holes into several different trees untilit finds a favorite tree. Sapsuckers will return to their favorite trees often and maynearly girdle them with peck holes. Although the holes normally heal over quickly,they cause defects and stain in the wood, reducing the value and quality of logs fromthese trees.

Control.-No measures are known that will prevent sapsucker damage. Warning: Donot remove the sapsuckers’ favorite trees or they will move to new trees. For otherbirds, erect several tall poles at various places within the plantation to provide alter-native perches for resting birds and to encourage the presence of predatory birds.

Domestic Livestock Swine and cattle injure trees by seeking shelter under trees or by grazing too neartrees. Their hooves can easily damage exposed roots near the groundline. Suchdamage may contribute to hollows in mature trees.

Control.-Place fences around trees in black walnut plantations destined for veneeror high-quality timber products.

Other Animals Beaver damage to black walnut is rare, although trees may be killed because offloodings caused by beaver dams. Plantations near streams in areas of large beaverpopulations are most susceptible.

Control.-Break up newly formed dams, trap out the beaver.

Barbara C. Weber and J. W. Van Sambeek

3


Record Keeping

Maintaining a permanent record of events, expenses, and sales from your walnutplantation or stand can be both enjoyable and profitable. Your permanent record canbe a big help when you figure your taxes or establish the value of timber for a saleor insurance loss. For starters, here’s what such a record should contain: a tree map;records of expenses, cultural treatments, tree growth and quality; frequent datedphotographs of your trees; plus other items of interest to you.

The Record Book

Tree Maps

Enter all records in a permanently bound, hard-covered notebook. This notebook willprobably get heavy use in your plantation or stand so make sure that its backings areof good quality.

An accurate map of your plantation or stand is an important part of your permanentrecord (fig. 1). Labelling the rows and trees within rows makes it possible to identifyindividual trees for keeping track of growth, form, and nut yields. Usually it is mostconvenient to letter the rows and number the trees. In natural stands irregular parallelrows can usually be drawn across the stand. Trees are then numbered according todistance from end of rows.

Figure 1.-Tree maps created by drawing irregular parallel rows through the stand make it easy to keep in-d i v i d u a l t r e e r e c o r d s .

Records Maintenance and Expenses.-Record when supplies are purchased or when any workis done in your plantation. For any work done, enter information such as what kind ofwork, who did it, how long it took, and what it cost. Remember to give yourselfminimum wages if you’re doing the work yourself. For ideas on what other expensesto include, see economic surveys like those published in the Walnut Council Bulletin.

Tree Growth.-Most owners will want to keep some records on how well their treesare growing, especially the crop trees. The most convenient measure is diameter atbreast height (4%. feet high on uphill side of tree). Mark a few trees throughout theplanting and measure them every few years to determine growth rates. When thetrees are large enough, paint letters or numbers directly on the tree with a light-colored latex tree paint to correspond with the letters or numbers on your map. Smalltrees can be marked with small stakes next to the trees. A permanent stake can bemade easily from #9 galvanized wire cut into 2 l / 2 - to 3-foot lengths with a small loopbent at one end of each to hold an identification tag (fig. 2). A slot cut across the end

S L O T T E D1” P IPE

M A C H I N I S T ’ S

Figure 2.-A permanent wirestake with a bent loop to hold ani d e n t i f i c a t i o n t a g c a n b e m a d eby bending a 3-foot length of No.9 galvanized wire around a slot-ted l-inch pipe (figure 2A) andplacing it near the base of eachtree (figure 2B).

of a l/2- to l-inch pipe held in a vise works well for holding the end of the wire as youbend the remainder around the end of the pipe. Do not place any metal (nails,fasteners, screws, etc.) in or on the trees. Any galvanized metal or iron in the tree willstain the wood and cause buyers to be cautious of any other timber you have forsale.

High-Value Trees.-By the time trees are 10 inches or larger in diameter, you will havepicked out some trees that contain high-quality veneer logs. Mark these trees with aunique identifying mark and enter tree location and your identifying mark into yourpermanent record. A record such as the one below will help establish a tree’s valuefor insurance purposes in case it is destroyed or stolen.

____-.--.__--- _- __-..______--.-Tree location Ht. to first Defects or other Int. log Estimated

Stand Row Tree D.B.H. large branch characteristics rule 1 / 4 ” stumpageno. B.F. value.___--..-____-..- -~-- .-__

Indian A 23 18” 10 feetCreek D 15 16” 16 feet

-

Some birdpeck140 $225180 $310

North C 5 20” 14 feet Pin knots 250 $375Terrace F 8 15” 16 feet - 160 $240_ _ _ _--_-~ . ..~ -.____---

Nut Trees.-When managing a stand for nuts and timber, keep records of nut yieldsand frequency of bearing. Also, record when grafts are made and if they’resuccessful.

J. W. Van Sambeek

3

Selling Black Walnut


NOTESWalnut timber buyers consider three things primarily when they look at a tree: size,straightness, and number of defects. Tree size includes diameter as well as heightparameters. A tall, clear, straight tree will probably have several merchantable logs inaddition to the butt log. Straightness is important because straight trees produce morelogs. Defects decrease the value of a tree and the logs in it. Examples of defects in-clude cat faces or limbs caused by a lack of branch pruning; seams caused bydisease, improper pruning, lightning, or frost damage; holes caused by insects or birdpeck; pin knots; hollows; and any ingrown metal objects.

The highest prices paid for black walnut timber are for large trees, 16 inches in d.b.h.or larger. Large trees that are exceptionally straight and defect-free can be used forveneer production; such trees command premium prices. Veneer-quality trees shouldcontain at least one 8%foot log at least 12 inches in diameter (inside bark) at thesmall end of the log. In areas of high demand, it is sometimes possible to sellsmaller trees, but such smaller timber also commands lower prices.

1. Determine Your You’ve found merchantable walnut in your stand and have decided to sell the timber.Business Strategy Now what do you do’!

First, determine the business strategy: how will the trees be sold, as lump-sum or bythe board-foot? Lump-sum sales may be appropriate if you want all the timber on atract removed, but you may want to sell only certain trees on your property. If so,number the trees with nontoxic tree-marking paint and record individual tree dimen-sions, estimated board-foot lumber content, and tree condition. You might also askyour local or State forestry agencies to “cruise” the potential sale trees and providesome “ball-park” estimates of the value of the timber. The extension agent or areaservice forester with your Department of Natural Resources may also be able to pro-vide a list of timber buyers in the area.

2. How to Makethe Sale

Most hardwood timber is bought on a one-to-one basis between the owner and thetimber buyer. However, this is not necessarily the best method for the landowner. Amore favorable approach for the timber owner involves inviting buyers to make sealedbids on the timber. Bid notices should clearly define the seller’s name, address, andphone number; location of trees to be harvested (legal description and local map);number of trees to be sold, dimensions, and how trees are identified; and special saleinstructions and requirements (such as stipulations about timing of harvest, etc.). Bidnotice should clearly state that only sealed bids will be accepted and should specifythe time and place when bids will be accepted, opened, and awarded.

3. Draw Up a SaleContract

Once the deal is closed, a timber sale contract should be drawn up. Although stan-dard contract forms are available, no standard contract can cover all circumstancesarising in all situations. Draw up the contract with advice from an attorney and a pro-fessional forester. The contract should stipulate that all timber sold should be paid forbefore it’s removed from the property. The buyer should be given a reasonableamount of time to remove the timber. Normally this is 12 to 18 months and should bestated in the contract although more time may be needed if unusual weather condi-tions occur. The timber sale contract should include:

a. Names and addresses of seller and buyer.b. Legal description and location of timber.c. Number of trees to be sold and how they are marked.d. The purchase price and how and when it is to be paid.e. Expiration date of the contract.f. Special instructions to the buyer about the prevention of fires; condition of fences,

roads, and other structures; and an understanding of what is expected if the re-maining timber is excessively damaged.

g. The seller’s guarantee that the buyer has access to the property for harvestingtimber.

h. Name of a third party agreeable to both seller and buyer to handle possible con-tract disputes.

i. The buyer’s proof of liability insurance coverage and workmen’s compensation.

The timber sale contract should be signed and dated by both seller and buyer, usual-ly in the presence of a notary public, although any mutually agreeable third party isacceptable.

Check the property on which the sale occurred several times during and after the log-ging operation to make sure that the buyer complied with the terms of the contract.Once you’ve determined that the terms of the timber sale contract have been met,provide the buyer with a written release from the contract.

George Rink

Date post:	09-Dec-2021
Category:	Documents
Upload:	others
View:	6 times
Download:	0 times

Finding Suitable Seed Guidelines for Locating Suitable Seeds

Documents